  Vincent Selhorst-Jones

Nonlinear Systems

Slide Duration:

Section 1: Introduction
Introduction to Precalculus

10m 3s

Intro
0:00
Title of the Course
0:06
Different Names for the Course
0:07
Precalculus
0:12
Math Analysis
0:14
Trigonometry
0:16
Algebra III
0:20
Geometry II
0:24
College Algebra
0:30
Same Concepts
0:36
How do the Lessons Work?
0:54
Introducing Concepts
0:56
Apply Concepts
1:04
Go through Examples
1:25
Who is this Course For?
1:38
Those Who Need eExtra Help with Class Work
1:52
Those Working on Material but not in Formal Class at School
1:54
Those Who Want a Refresher
2:00
Try to Watch the Whole Lesson
2:20
Understanding is So Important
3:56
What to Watch First
5:26
Lesson #2: Sets, Elements, and Numbers
5:30
Lesson #7: Idea of a Function
5:33
Lesson #6: Word Problems
6:04
What to Watch First, cont.
6:46
Lesson #2: Sets, Elements and Numbers
6:56
Lesson #3: Variables, Equations, and Algebra
6:58
Lesson #4: Coordinate Systems
7:00
Lesson #5: Midpoint, Distance, the Pythagorean Theorem and Slope
7:02
Lesson #6: Word Problems
7:10
Lesson #7: Idea of a Function
7:12
Lesson #8: Graphs
7:14
Graphing Calculator Appendix
7:40
What to Watch Last
8:46
Let's get Started!
9:48
Sets, Elements, & Numbers

45m 11s

Intro
0:00
Introduction
0:05
Sets and Elements
1:19
Set
1:20
Element
1:23
Name a Set
2:20
Order The Elements Appear In Has No Effect on the Set
2:55
Describing/ Defining Sets
3:28
Directly Say All the Elements
3:36
Clearly Describing All the Members of the Set
3:55
Describing the Quality (or Qualities) Each member Of the Set Has In Common
4:32
Symbols: 'Element of' and 'Subset of'
6:01
Symbol is ∈
6:03
Subset Symbol is ⊂
6:35
Empty Set
8:07
Symbol is ∅
8:20
Since It's Empty, It is a Subset of All Sets
8:44
Union and Intersection
9:54
Union Symbol is ∪
10:08
Intersection Symbol is ∩
10:18
Sets Can Be Weird Stuff
12:26
Can Have Elements in a Set
12:50
We Can Have Infinite Sets
13:09
Example
13:22
Consider a Set Where We Take a Word and Then Repeat It An Ever Increasing Number of Times
14:08
This Set Has Infinitely Many Distinct Elements
14:40
Numbers as Sets
16:03
Natural Numbers ℕ
16:16
Including 0 and the Negatives ℤ
18:13
Rational Numbers ℚ
19:27
Can Express Rational Numbers with Decimal Expansions
22:05
Irrational Numbers
23:37
Real Numbers ℝ: Put the Rational and Irrational Numbers Together
25:15
Interval Notation and the Real Numbers
26:45
Include the End Numbers
27:06
Exclude the End Numbers
27:33
Example
28:28
Interval Notation: Infinity
29:09
Use -∞ or ∞ to Show an Interval Going on Forever in One Direction or the Other
29:14
Always Use Parentheses
29:50
Examples
30:27
Example 1
31:23
Example 2
35:26
Example 3
38:02
Example 4
42:21
Variables, Equations, & Algebra

35m 31s

Intro
0:00
What is a Variable?
0:05
A Variable is a Placeholder for a Number
0:11
Affects the Output of a Function or a Dependent Variable
0:24
Naming Variables
1:51
Useful to Use Symbols
2:21
What is a Constant?
4:14
A Constant is a Fixed, Unchanging Number
4:28
We Might Refer to a Symbol Representing a Number as a Constant
4:51
What is a Coefficient?
5:33
A Coefficient is a Multiplicative Factor on a Variable
5:37
Not All Coefficients are Constants
5:51
Expressions and Equations
6:42
An Expression is a String of Mathematical Symbols That Make Sense Used Together
7:05
An Equation is a Statement That Two Expression Have the Same Value
8:20
The Idea of Algebra
8:51
Equality
8:59
If Two Things Are the Same *Equal), Then We Can Do the Exact Same Operation to Both and the Results Will Be the Same
9:41
Always Do The Exact Same Thing to Both Sides
12:22
Solving Equations
13:23
When You Are Asked to Solve an Equation, You Are Being Asked to Solve for Something
13:33
Look For What Values Makes the Equation True
13:38
Isolate the Variable by Doing Algebra
14:37
Order of Operations
16:02
Why Certain Operations are Grouped
17:01
When You Don't Have to Worry About Order
17:39
Distributive Property
18:15
It Allows Multiplication to Act Over Addition in Parentheses
18:23
We Can Use the Distributive Property in Reverse to Combine Like Terms
19:05
Substitution
20:03
Use Information From One Equation in Another Equation
20:07
20:44
Example 1
23:17
Example 2
25:49
Example 3
28:11
Example 4
30:02
Coordinate Systems

35m 2s

Intro
0:00
Inherent Order in ℝ
0:05
Real Numbers Come with an Inherent Order
0:11
Positive Numbers
0:21
Negative Numbers
0:58
'Less Than' and 'Greater Than'
2:04
2:56
Inequality
4:06
Less Than or Equal and Greater Than or Equal
4:51
One Dimension: The Number Line
5:36
Graphically Represent ℝ on a Number Line
5:43
Note on Infinities
5:57
With the Number Line, We Can Directly See the Order We Put on ℝ
6:35
Ordered Pairs
7:22
Example
7:34
Allows Us to Talk About Two Numbers at the Same Time
9:41
Ordered Pairs of Real Numbers Cannot be Put Into an Order Like we Did with ℝ
10:41
Two Dimensions: The Plane
13:13
We Can Represent Ordered Pairs with the Plane
13:24
Intersection is known as the Origin
14:31
Plotting the Point
14:32
Plane = Coordinate Plane = Cartesian Plane = ℝ²
17:46
18:50
19:04
19:21
20:04
20:20
Three Dimensions: Space
21:02
Create Ordered Triplets
21:09
Visually Represent This
21:19
Three-Dimension = Space = ℝ³
21:47
Higher Dimensions
22:24
If We Have n Dimensions, We Call It n-Dimensional Space or ℝ to the nth Power
22:31
We Can Represent Places In This n-Dimensional Space As Ordered Groupings of n Numbers
22:41
Hard to Visualize Higher Dimensional Spaces
23:18
Example 1
25:07
Example 2
26:10
Example 3
28:58
Example 4
31:05
Midpoints, Distance, the Pythagorean Theorem, & Slope

48m 43s

Intro
0:00
Introduction
0:07
Midpoint: One Dimension
2:09
Example of Something More Complex
2:31
Use the Idea of a Middle
3:28
Find the Midpoint of Arbitrary Values a and b
4:17
How They're Equivalent
5:05
Official Midpoint Formula
5:46
Midpoint: Two Dimensions
6:19
The Midpoint Must Occur at the Horizontal Middle and the Vertical Middle
6:38
Arbitrary Pair of Points Example
7:25
Distance: One Dimension
9:26
Absolute Value
10:54
Idea of Forcing Positive
11:06
Distance: One Dimension, Formula
11:47
Distance Between Arbitrary a and b
11:48
Absolute Value Helps When the Distance is Negative
12:41
Distance Formula
12:58
The Pythagorean Theorem
13:24
a²+b²=c²
13:50
Distance: Two Dimensions
14:59
Break Into Horizontal and Vertical Parts and then Use the Pythagorean Theorem
15:16
Distance Between Arbitrary Points (x₁,y₁) and (x₂,y₂)
16:21
Slope
19:30
Slope is the Rate of Change
19:41
m = rise over run
21:27
Slope Between Arbitrary Points (x₁,y₁) and (x₂,y₂)
22:31
Interpreting Slope
24:12
Positive Slope and Negative Slope
25:40
m=1, m=0, m=-1
26:48
Example 1
28:25
Example 2
31:42
Example 3
36:40
Example 4
42:48
Word Problems

56m 31s

Intro
0:00
Introduction
0:05
What is a Word Problem?
0:45
Describes Any Problem That Primarily Gets Its Ideas Across With Words Instead of Math Symbols
0:48
Requires Us to Think
1:32
Why Are They So Hard?
2:11
Reason 1: No Simple Formula to Solve Them
2:16
Reason 2: Harder to Teach Word Problems
2:47
You Can Learn How to Do Them!
3:51
7:57
'But I'm Never Going to Use This In Real Life'
9:46
Solving Word Problems
12:58
First: Understand the Problem
13:37
Second: What Are You Looking For?
14:33
Third: Set Up Relationships
16:21
Fourth: Solve It!
17:48
Summary of Method
19:04
Examples on Things Other Than Math
20:21
Math-Specific Method: What You Need Now
25:30
Understand What the Problem is Talking About
25:37
Set Up and Name Any Variables You Need to Know
25:56
Set Up Equations Connecting Those Variables to the Information in the Problem Statement
26:02
Use the Equations to Solve for an Answer
26:14
Tip
26:58
Draw Pictures
27:22
Breaking Into Pieces
28:28
Try Out Hypothetical Numbers
29:52
Student Logic
31:27
Jump In!
32:40
Example 1
34:03
Example 2
39:15
Example 3
44:22
Example 4
50:24
Section 2: Functions
Idea of a Function

39m 54s

Intro
0:00
Introduction
0:04
What is a Function?
1:06
A Visual Example and Non-Example
1:30
Function Notation
3:47
f(x)
4:05
Express What Sets the Function Acts On
5:45
Metaphors for a Function
6:17
Transformation
6:28
Map
7:17
Machine
8:56
Same Input Always Gives Same Output
10:01
If We Put the Same Input Into a Function, It Will Always Produce the Same Output
10:11
Example of Something That is Not a Function
11:10
A Non-Numerical Example
12:10
The Functions We Will Use
15:05
Unless Told Otherwise, We Will Assume Every Function Takes in Real Numbers and Outputs Real Numbers
15:11
Usually Told the Rule of a Given Function
15:27
How To Use a Function
16:18
Apply the Rule to Whatever Our Input Value Is
16:28
Make Sure to Wrap Your Substitutions in Parentheses
17:09
Functions and Tables
17:36
Table of Values, Sometimes Called a T-Table
17:46
Example
17:56
Domain: What Goes In
18:55
The Domain is the Set of all Inputs That the Function Can Accept
18:56
Example
19:40
Range: What Comes Out
21:27
The Range is the Set of All Possible Outputs a Function Can Assign
21:34
Example
21:49
Another Example Would Be Our Initial Function From Earlier in This Lesson
22:29
Example 1
23:45
Example 2
25:22
Example 3
27:27
Example 4
29:23
Example 5
33:33
Graphs

58m 26s

Intro
0:00
Introduction
0:04
How to Interpret Graphs
1:17
Input / Independent Variable
1:47
Output / Dependent Variable
2:00
Graph as Input ⇒ Output
2:23
One Way to Think of a Graph: See What Happened to Various Inputs
2:25
Example
2:47
Graph as Location of Solution
4:20
A Way to See Solutions
4:36
Example
5:20
Which Way Should We Interpret?
7:13
Easiest to Think In Terms of How Inputs Are Mapped to Outputs
7:20
Sometimes It's Easier to Think In Terms of Solutions
8:39
Pay Attention to Axes
9:50
Axes Tell Where the Graph Is and What Scale It Has
10:09
Often, The Axes Will Be Square
10:14
Example
12:06
Arrows or No Arrows?
16:07
Will Not Use Arrows at the End of Our Graphs
17:13
Graph Stops Because It Hits the Edge of the Graphing Axes, Not Because the Function Stops
17:18
How to Graph
19:47
Plot Points
20:07
Connect with Curves
21:09
If You Connect with Straight Lines
21:44
Graphs of Functions are Smooth
22:21
More Points ⇒ More Accurate
23:38
Vertical Line Test
27:44
If a Vertical Line Could Intersect More Than One Point On a Graph, It Can Not Be the Graph of a Function
28:41
Every Point on a Graph Tells Us Where the x-Value Below is Mapped
30:07
Domain in Graphs
31:37
The Domain is the Set of All Inputs That a Function Can Accept
31:44
Be Aware That Our Function Probably Continues Past the Edge of Our 'Viewing Window'
33:19
Range in Graphs
33:53
Graphing Calculators: Check the Appendix!
36:55
Example 1
38:37
Example 2
45:19
Example 3
50:41
Example 4
53:28
Example 5
55:50
Properties of Functions

48m 49s

Intro
0:00
Introduction
0:05
Increasing Decreasing Constant
0:43
Looking at a Specific Graph
1:15
Increasing Interval
2:39
Constant Function
4:15
Decreasing Interval
5:10
Find Intervals by Looking at the Graph
5:32
Intervals Show x-values; Write in Parentheses
6:39
Maximum and Minimums
8:48
Relative (Local) Max/Min
10:20
Formal Definition of Relative Maximum
12:44
Formal Definition of Relative Minimum
13:05
Max/Min, More Terms
14:18
Definition of Extrema
15:01
Average Rate of Change
16:11
Drawing a Line for the Average Rate
16:48
Using the Slope of the Secant Line
17:36
Slope in Function Notation
18:45
Zeros/Roots/x-intercepts
19:45
What Zeros in a Function Mean
20:25
Even Functions
22:30
Odd Functions
24:36
Even/Odd Functions and Graphs
26:28
Example of an Even Function
27:12
Example of an Odd Function
28:03
Example 1
29:35
Example 2
33:07
Example 3
40:32
Example 4
42:34
Function Petting Zoo

29m 20s

Intro
0:00
Introduction
0:04
Don't Forget that Axes Matter!
1:44
The Constant Function
2:40
The Identity Function
3:44
The Square Function
4:40
The Cube Function
5:44
The Square Root Function
6:51
The Reciprocal Function
8:11
The Absolute Value Function
10:19
The Trigonometric Functions
11:56
f(x)=sin(x)
12:12
f(x)=cos(x)
12:24
Alternate Axes
12:40
The Exponential and Logarithmic Functions
13:35
Exponential Functions
13:44
Logarithmic Functions
14:24
Alternating Axes
15:17
Transformations and Compositions
16:08
Example 1
17:52
Example 2
18:33
Example 3
20:24
Example 4
26:07
Transformation of Functions

48m 35s

Intro
0:00
Introduction
0:04
Vertical Shift
1:12
Graphical Example
1:21
A Further Explanation
2:16
Vertical Stretch/Shrink
3:34
Graph Shrinks
3:46
Graph Stretches
3:51
A Further Explanation
5:07
Horizontal Shift
6:49
Moving the Graph to the Right
7:28
Moving the Graph to the Left
8:12
A Further Explanation
8:19
Understanding Movement on the x-axis
8:38
Horizontal Stretch/Shrink
12:59
Shrinking the Graph
13:40
Stretching the Graph
13:48
A Further Explanation
13:55
Understanding Stretches from the x-axis
14:12
Vertical Flip (aka Mirror)
16:55
Example Graph
17:07
Multiplying the Vertical Component by -1
17:18
Horizontal Flip (aka Mirror)
18:43
Example Graph
19:01
Multiplying the Horizontal Component by -1
19:54
Summary of Transformations
22:11
Stacking Transformations
24:46
Order Matters
25:20
Transformation Example
25:52
Example 1
29:21
Example 2
34:44
Example 3
38:10
Example 4
43:46
Composite Functions

33m 24s

Intro
0:00
Introduction
0:04
Arithmetic Combinations
0:40
Basic Operations
1:20
Definition of the Four Arithmetic Combinations
1:40
Composite Functions
2:53
The Function as a Machine
3:32
Function Compositions as Multiple Machines
3:59
Notation for Composite Functions
4:46
Two Formats
6:02
Another Visual Interpretation
7:17
How to Use Composite Functions
8:21
Example of on Function acting on Another
9:17
Example 1
11:03
Example 2
15:27
Example 3
21:11
Example 4
27:06
Piecewise Functions

51m 42s

Intro
0:00
Introduction
0:04
Analogies to a Piecewise Function
1:16
Different Potatoes
1:41
Factory Production
2:27
Notations for Piecewise Functions
3:39
Notation Examples from Analogies
6:11
Example of a Piecewise (with Table)
7:24
Example of a Non-Numerical Piecewise
11:35
Graphing Piecewise Functions
14:15
Graphing Piecewise Functions, Example
16:26
Continuous Functions
16:57
Statements of Continuity
19:30
Example of Continuous and Non-Continuous Graphs
20:05
Interesting Functions: the Step Function
22:00
Notation for the Step Function
22:40
How the Step Function Works
22:56
Graph of the Step Function
25:30
Example 1
26:22
Example 2
28:49
Example 3
36:50
Example 4
46:11
Inverse Functions

49m 37s

Intro
0:00
Introduction
0:04
Analogy by picture
1:10
How to Denote the inverse
1:40
What Comes out of the Inverse
1:52
Requirement for Reversing
2:02
2:12
The Importance of Information
2:45
One-to-One
4:04
Requirement for Reversibility
4:21
When a Function has an Inverse
4:43
One-to-One
5:13
Not One-to-One
5:50
Not a Function
6:19
Horizontal Line Test
7:01
How to the test Works
7:12
One-to-One
8:12
Not One-to-One
8:45
Definition: Inverse Function
9:12
Formal Definition
9:21
Caution to Students
10:02
Domain and Range
11:12
Finding the Range of the Function Inverse
11:56
Finding the Domain of the Function Inverse
12:11
Inverse of an Inverse
13:09
Its just x!
13:26
Proof
14:03
Graphical Interpretation
17:07
Horizontal Line Test
17:20
Graph of the Inverse
18:04
Swapping Inputs and Outputs to Draw Inverses
19:02
How to Find the Inverse
21:03
What We Are Looking For
21:21
Reversing the Function
21:38
A Method to Find Inverses
22:33
Check Function is One-to-One
23:04
Swap f(x) for y
23:25
Interchange x and y
23:41
Solve for y
24:12
Replace y with the inverse
24:40
25:01
Keeping Step 2 and 3 Straight
25:44
Switching to Inverse
26:12
Checking Inverses
28:52
How to Check an Inverse
29:06
Quick Example of How to Check
29:56
Example 1
31:48
Example 2
34:56
Example 3
39:29
Example 4
46:19
Variation Direct and Inverse

28m 49s

Intro
0:00
Introduction
0:06
Direct Variation
1:14
Same Direction
1:21
Common Example: Groceries
1:56
Different Ways to Say that Two Things Vary Directly
2:28
Basic Equation for Direct Variation
2:55
Inverse Variation
3:40
Opposite Direction
3:50
Common Example: Gravity
4:53
Different Ways to Say that Two Things Vary Indirectly
5:48
Basic Equation for Indirect Variation
6:33
Joint Variation
7:27
Equation for Joint Variation
7:53
Explanation of the Constant
8:48
Combined Variation
9:35
Gas Law as a Combination
9:44
Single Constant
10:33
Example 1
10:49
Example 2
13:34
Example 3
15:39
Example 4
19:48
Section 3: Polynomials
Intro to Polynomials

38m 41s

Intro
0:00
Introduction
0:04
Definition of a Polynomial
1:04
Starting Integer
2:06
Structure of a Polynomial
2:49
The a Constants
3:34
Polynomial Function
5:13
Polynomial Equation
5:23
Polynomials with Different Variables
5:36
Degree
6:23
Informal Definition
6:31
Find the Largest Exponent Variable
6:44
Quick Examples
7:36
Special Names for Polynomials
8:59
Based on the Degree
9:23
Based on the Number of Terms
10:12
Distributive Property (aka 'FOIL')
11:37
Basic Distributive Property
12:21
Distributing Two Binomials
12:55
Longer Parentheses
15:12
Reverse: Factoring
17:26
Long-Term Behavior of Polynomials
17:48
Examples
18:13
Controlling Term--Term with the Largest Exponent
19:33
Positive and Negative Coefficients on the Controlling Term
20:21
22:07
Even Degree, Positive Coefficient
22:13
Even Degree, Negative Coefficient
22:39
Odd Degree, Positive Coefficient
23:09
Odd Degree, Negative Coefficient
23:27
Example 1
25:11
Example 2
27:16
Example 3
31:16
Example 4
34:41
Roots (Zeros) of Polynomials

41m 7s

Intro
0:00
Introduction
0:05
Roots in Graphs
1:17
The x-intercepts
1:33
How to Remember What 'Roots' Are
1:50
Naïve Attempts
2:31
Isolating Variables
2:45
Failures of Isolating Variables
3:30
Missing Solutions
4:59
Factoring: How to Find Roots
6:28
How Factoring Works
6:36
Why Factoring Works
7:20
Steps to Finding Polynomial Roots
9:21
Factoring: How to Find Roots CAUTION
10:08
Factoring is Not Easy
11:32
13:08
13:21
Form of Factored Binomials
13:38
Factoring Examples
14:40
16:58
Factoring Higher Degree Polynomials
18:19
Factoring a Cubic
18:32
19:04
Factoring: Roots Imply Factors
19:54
Where a Root is, A Factor Is
20:01
How to Use Known Roots to Make Factoring Easier
20:35
Not all Polynomials Can be Factored
22:30
Irreducible Polynomials
23:27
Complex Numbers Help
23:55
Max Number of Roots/Factors
24:57
Limit to Number of Roots Equal to the Degree
25:18
Why there is a Limit
25:25
Max Number of Peaks/Valleys
26:39
Shape Information from Degree
26:46
Example Graph
26:54
Max, But Not Required
28:00
Example 1
28:37
Example 2
31:21
Example 3
36:12
Example 4
38:40
Completing the Square and the Quadratic Formula

39m 43s

Intro
0:00
Introduction
0:05
Square Roots and Equations
0:51
Taking the Square Root to Find the Value of x
0:55
Getting the Positive and Negative Answers
1:05
Completing the Square: Motivation
2:04
Polynomials that are Easy to Solve
2:20
Making Complex Polynomials Easy to Solve
3:03
Steps to Completing the Square
4:30
Completing the Square: Method
7:22
Move C over
7:35
Divide by A
7:44
Find r
7:59
Add to Both Sides to Complete the Square
8:49
9:56
11:38
Derivation
11:43
Final Form
12:23
13:38
How Many Roots?
14:53
The Discriminant
15:47
What the Discriminant Tells Us: How Many Roots
15:58
How the Discriminant Works
16:30
Example 1: Complete the Square
18:24
22:00
Example 3: Solve for Zeroes
25:28
Example 4: Using the Quadratic Formula
30:52

45m 34s

Intro
0:00
Introduction
0:05
Parabolas
0:35
Examples of Different Parabolas
1:06
Axis of Symmetry and Vertex
1:28
Drawing an Axis of Symmetry
1:51
Placing the Vertex
2:28
Looking at the Axis of Symmetry and Vertex for other Parabolas
3:09
Transformations
4:18
Reviewing Transformation Rules
6:28
Note the Different Horizontal Shift Form
7:45
8:54
The Constants: k, h, a
9:05
Transformations Formed
10:01
Analyzing Different Parabolas
10:10
Switching Forms by Completing the Square
11:43
Vertex of a Parabola
16:30
Vertex at (h, k)
16:47
Vertex in Terms of a, b, and c Coefficients
17:28
Minimum/Maximum at Vertex
18:19
When a is Positive
18:25
When a is Negative
18:52
Axis of Symmetry
19:54
Incredibly Minor Note on Grammar
20:52
Example 1
21:48
Example 2
26:35
Example 3
28:55
Example 4
31:40
Intermediate Value Theorem and Polynomial Division

46m 8s

Intro
0:00
Introduction
0:05
Reminder: Roots Imply Factors
1:32
The Intermediate Value Theorem
3:41
The Basis: U between a and b
4:11
U is on the Function
4:52
Intermediate Value Theorem, Proof Sketch
5:51
If Not True, the Graph Would Have to Jump
5:58
But Graph is Defined as Continuous
6:43
Finding Roots with the Intermediate Value Theorem
7:01
Picking a and b to be of Different Signs
7:10
Must Be at Least One Root
7:46
Dividing a Polynomial
8:16
Using Roots and Division to Factor
8:38
Long Division Refresher
9:08
The Division Algorithm
12:18
How It Works to Divide Polynomials
12:37
The Parts of the Equation
13:24
Rewriting the Equation
14:47
Polynomial Long Division
16:20
Polynomial Long Division In Action
16:29
One Step at a Time
20:51
Synthetic Division
22:46
Setup
23:11
Synthetic Division, Example
24:44
Which Method Should We Use
26:39
26:49
27:13
Example 1
29:24
Example 2
31:27
Example 3
36:22
Example 4
40:55
Complex Numbers

45m 36s

Intro
0:00
Introduction
0:04
A Wacky Idea
1:02
The Definition of the Imaginary Number
1:22
How it Helps Solve Equations
2:20
Square Roots and Imaginary Numbers
3:15
Complex Numbers
5:00
Real Part and Imaginary Part
5:20
When Two Complex Numbers are Equal
6:10
6:40
Deal with Real and Imaginary Parts Separately
7:36
Two Quick Examples
7:54
Multiplication
9:07
FOIL Expansion
9:14
Note What Happens to the Square of the Imaginary Number
9:41
Two Quick Examples
10:22
Division
11:27
Complex Conjugates
13:37
Getting Rid of i
14:08
How to Denote the Conjugate
14:48
Division through Complex Conjugates
16:11
Multiply by the Conjugate of the Denominator
16:28
Example
17:46
19:24
20:12
Conjugate Pairs
20:37
But Are the Complex Numbers 'Real'?
21:27
What Makes a Number Legitimate
25:38
Where Complex Numbers are Used
27:20
Still, We Won't See Much of C
29:05
Example 1
30:30
Example 2
33:15
Example 3
38:12
Example 4
42:07
Fundamental Theorem of Algebra

19m 9s

Intro
0:00
Introduction
0:05
Idea: Hidden Roots
1:16
Roots in Complex Form
1:42
All Polynomials Have Roots
2:08
Fundamental Theorem of Algebra
2:21
Where Are All the Imaginary Roots, Then?
3:17
All Roots are Complex
3:45
Real Numbers are a Subset of Complex Numbers
3:59
The n Roots Theorem
5:01
For Any Polynomial, Its Degree is Equal to the Number of Roots
5:11
Equivalent Statement
5:24
6:29
Non-Distinct Roots
6:59
Denoting Multiplicity
7:20
7:41
8:55
9:59
Proof Sketch of n Roots Theorem
10:45
First Root
11:36
Second Root
13:23
Continuation to Find all Roots
16:00
Section 4: Rational Functions
Rational Functions and Vertical Asymptotes

33m 22s

Intro
0:00
Introduction
0:05
Definition of a Rational Function
1:20
Examples of Rational Functions
2:30
Why They are Called 'Rational'
2:47
Domain of a Rational Function
3:15
Undefined at Denominator Zeros
3:25
Otherwise all Reals
4:16
Investigating a Fundamental Function
4:50
The Domain of the Function
5:04
What Occurs at the Zeroes of the Denominator
5:20
Idea of a Vertical Asymptote
6:23
What's Going On?
6:58
Approaching x=0 from the left
7:32
Approaching x=0 from the right
8:34
Dividing by Very Small Numbers Results in Very Large Numbers
9:31
Definition of a Vertical Asymptote
10:05
Vertical Asymptotes and Graphs
11:15
Drawing Asymptotes by Using a Dashed Line
11:27
The Graph Can Never Touch Its Undefined Point
12:00
Not All Zeros Give Asymptotes
13:02
Special Cases: When Numerator and Denominator Go to Zero at the Same Time
14:58
Cancel out Common Factors
15:49
How to Find Vertical Asymptotes
16:10
Figure out What Values Are Not in the Domain of x
16:24
Determine if the Numerator and Denominator Share Common Factors and Cancel
16:45
Find Denominator Roots
17:33
Note if Asymptote Approaches Negative or Positive Infinity
18:06
Example 1
18:57
Example 2
21:26
Example 3
23:04
Example 4
30:01
Horizontal Asymptotes

34m 16s

Intro
0:00
Introduction
0:05
Investigating a Fundamental Function
0:53
What Happens as x Grows Large
1:00
Different View
1:12
Idea of a Horizontal Asymptote
1:36
What's Going On?
2:24
What Happens as x Grows to a Large Negative Number
2:49
What Happens as x Grows to a Large Number
3:30
Dividing by Very Large Numbers Results in Very Small Numbers
3:52
Example Function
4:41
Definition of a Vertical Asymptote
8:09
Expanding the Idea
9:03
What's Going On?
9:48
What Happens to the Function in the Long Run?
9:51
Rewriting the Function
10:13
Definition of a Slant Asymptote
12:09
Symbolical Definition
12:30
Informal Definition
12:45
Beyond Slant Asymptotes
13:03
Not Going Beyond Slant Asymptotes
14:39
Horizontal/Slant Asymptotes and Graphs
15:43
How to Find Horizontal and Slant Asymptotes
16:52
How to Find Horizontal Asymptotes
17:12
Expand the Given Polynomials
17:18
Compare the Degrees of the Numerator and Denominator
17:40
How to Find Slant Asymptotes
20:05
Slant Asymptotes Exist When n+m=1
20:08
Use Polynomial Division
20:24
Example 1
24:32
Example 2
25:53
Example 3
26:55
Example 4
29:22
Graphing Asymptotes in a Nutshell

49m 7s

Intro
0:00
Introduction
0:05
A Process for Graphing
1:22
1. Factor Numerator and Denominator
1:50
2. Find Domain
2:53
3. Simplifying the Function
3:59
4. Find Vertical Asymptotes
4:59
5. Find Horizontal/Slant Asymptotes
5:24
6. Find Intercepts
7:35
7. Draw Graph (Find Points as Necessary)
9:21
Draw Graph Example
11:21
Vertical Asymptote
11:41
Horizontal Asymptote
11:50
Other Graphing
12:16
Test Intervals
15:08
Example 1
17:57
Example 2
23:01
Example 3
29:02
Example 4
33:37
Partial Fractions

44m 56s

Intro
0:00
Introduction: Idea
0:04
Introduction: Prerequisites and Uses
1:57
Proper vs. Improper Polynomial Fractions
3:11
Possible Things in the Denominator
4:38
Linear Factors
6:16
Example of Linear Factors
7:03
Multiple Linear Factors
7:48
8:25
9:26
9:49
Mixing Factor Types
10:28
Figuring Out the Numerator
11:10
How to Solve for the Constants
11:30
Quick Example
11:40
Example 1
14:29
Example 2
18:35
Example 3
20:33
Example 4
28:51
Section 5: Exponential & Logarithmic Functions
Understanding Exponents

35m 17s

Intro
0:00
Introduction
0:05
Fundamental Idea
1:46
Expanding the Idea
2:28
Multiplication of the Same Base
2:40
Exponents acting on Exponents
3:45
Different Bases with the Same Exponent
4:31
To the Zero
5:35
To the First
5:45
Fundamental Rule with the Zero Power
6:35
To the Negative
7:45
Any Number to a Negative Power
8:14
A Fraction to a Negative Power
9:58
Division with Exponential Terms
10:41
To the Fraction
11:33
Square Root
11:58
Any Root
12:59
Summary of Rules
14:38
To the Irrational
17:21
Example 1
20:34
Example 2
23:42
Example 3
27:44
Example 4
31:44
Example 5
33:15
Exponential Functions

47m 4s

Intro
0:00
Introduction
0:05
Definition of an Exponential Function
0:48
Definition of the Base
1:02
Restrictions on the Base
1:16
Computing Exponential Functions
2:29
Harder Computations
3:10
When to Use a Calculator
3:21
Graphing Exponential Functions: a>1
6:02
Three Examples
6:13
What to Notice on the Graph
7:44
A Story
8:27
Story Diagram
9:15
Increasing Exponentials
11:29
Story Morals
14:40
Application: Compound Interest
15:15
Compounding Year after Year
16:01
Function for Compounding Interest
16:51
A Special Number: e
20:55
Expression for e
21:28
Where e stabilizes
21:55
Application: Continuously Compounded Interest
24:07
Equation for Continuous Compounding
24:22
Exponential Decay 0<a<1
25:50
Three Examples
26:11
Why they 'lose' value
26:54
Example 1
27:47
Example 2
33:11
Example 3
36:34
Example 4
41:28
Introduction to Logarithms

40m 31s

Intro
0:00
Introduction
0:04
Definition of a Logarithm, Base 2
0:51
Log 2 Defined
0:55
Examples
2:28
Definition of a Logarithm, General
3:23
Examples of Logarithms
5:15
Problems with Unusual Bases
7:38
Shorthand Notation: ln and log
9:44
base e as ln
10:01
base 10 as log
10:34
Calculating Logarithms
11:01
using a calculator
11:34
issues with other bases
11:58
Graphs of Logarithms
13:21
Three Examples
13:29
Slow Growth
15:19
Logarithms as Inverse of Exponentiation
16:02
Using Base 2
16:05
General Case
17:10
Looking More Closely at Logarithm Graphs
19:16
The Domain of Logarithms
20:41
21:08
The Alternate
24:00
Example 1
25:59
Example 2
30:03
Example 3
32:49
Example 4
37:34
Properties of Logarithms

42m 33s

Intro
0:00
Introduction
0:04
Basic Properties
1:12
Inverse--log(exp)
1:43
A Key Idea
2:44
What We Get through Exponentiation
3:18
B Always Exists
4:50
Inverse--exp(log)
5:53
Logarithm of a Power
7:44
Logarithm of a Product
10:07
Logarithm of a Quotient
13:48
Caution! There Is No Rule for loga(M+N)
16:12
Summary of Properties
17:42
Change of Base--Motivation
20:17
No Calculator Button
20:59
A Specific Example
21:45
Simplifying
23:45
Change of Base--Formula
24:14
Example 1
25:47
Example 2
29:08
Example 3
31:14
Example 4
34:13
Solving Exponential and Logarithmic Equations

34m 10s

Intro
0:00
Introduction
0:05
One to One Property
1:09
Exponential
1:26
Logarithmic
1:44
Specific Considerations
2:02
One-to-One Property
3:30
Solving by One-to-One
4:11
Inverse Property
6:09
Solving by Inverses
7:25
Dealing with Equations
7:50
Example of Taking an Exponent or Logarithm of an Equation
9:07
A Useful Property
11:57
Bring Down Exponents
12:01
Try to Simplify
13:20
Extraneous Solutions
13:45
Example 1
16:37
Example 2
19:39
Example 3
21:37
Example 4
26:45
Example 5
29:37
Application of Exponential and Logarithmic Functions

48m 46s

Intro
0:00
Introduction
0:06
Applications of Exponential Functions
1:07
A Secret!
2:17
Natural Exponential Growth Model
3:07
Figure out r
3:34
A Secret!--Why Does It Work?
4:44
e to the r Morphs
4:57
Example
5:06
Applications of Logarithmic Functions
8:32
Examples
8:43
What Logarithms are Useful For
9:53
Example 1
11:29
Example 2
15:30
Example 3
26:22
Example 4
32:05
Example 5
39:19
Section 6: Trigonometric Functions
Angles

39m 5s

Intro
0:00
Degrees
0:22
Circle is 360 Degrees
0:48
Splitting a Circle
1:13
2:08
2:31
2:52
Half-Circle and Right Angle
4:00
6:24
6:52
Coterminal, Complementary, Supplementary Angles
7:23
Coterminal Angles
7:30
Complementary Angles
9:40
Supplementary Angles
10:08
Example 1: Dividing a Circle
10:38
Example 2: Converting Between Degrees and Radians
11:56
Example 3: Quadrants and Coterminal Angles
14:18
Extra Example 1: Common Angle Conversions
-1
Extra Example 2: Quadrants and Coterminal Angles
-2
Sine and Cosine Functions

43m 16s

Intro
0:00
Sine and Cosine
0:15
Unit Circle
0:22
Coordinates on Unit Circle
1:03
Right Triangles
1:52
2:25
Master Right Triangle Formula: SOHCAHTOA
2:48
Odd Functions, Even Functions
4:40
Example: Odd Function
4:56
Example: Even Function
7:30
Example 1: Sine and Cosine
10:27
Example 2: Graphing Sine and Cosine Functions
14:39
Example 3: Right Triangle
21:40
Example 4: Odd, Even, or Neither
26:01
Extra Example 1: Right Triangle
-1
Extra Example 2: Graphing Sine and Cosine Functions
-2
Sine and Cosine Values of Special Angles

33m 5s

Intro
0:00
45-45-90 Triangle and 30-60-90 Triangle
0:08
45-45-90 Triangle
0:21
30-60-90 Triangle
2:06
Mnemonic: All Students Take Calculus (ASTC)
5:21
Using the Unit Circle
5:59
New Angles
6:21
9:43
Mnemonic: All Students Take Calculus
10:13
13:11
16:48
Example 3: All Angles and Quadrants
20:21
Extra Example 1: Convert, Quadrant, Sine/Cosine
-1
Extra Example 2: All Angles and Quadrants
-2
Modified Sine Waves: Asin(Bx+C)+D and Acos(Bx+C)+D

52m 3s

Intro
0:00
Amplitude and Period of a Sine Wave
0:38
Sine Wave Graph
0:58
Amplitude: Distance from Middle to Peak
1:18
Peak: Distance from Peak to Peak
2:41
Phase Shift and Vertical Shift
4:13
Phase Shift: Distance Shifted Horizontally
4:16
Vertical Shift: Distance Shifted Vertically
6:48
Example 1: Amplitude/Period/Phase and Vertical Shift
8:04
Example 2: Amplitude/Period/Phase and Vertical Shift
17:39
Example 3: Find Sine Wave Given Attributes
25:23
Extra Example 1: Amplitude/Period/Phase and Vertical Shift
-1
Extra Example 2: Find Cosine Wave Given Attributes
-2
Tangent and Cotangent Functions

36m 4s

Intro
0:00
Tangent and Cotangent Definitions
0:21
Tangent Definition
0:25
Cotangent Definition
0:47
Master Formula: SOHCAHTOA
1:01
Mnemonic
1:16
Tangent and Cotangent Values
2:29
Remember Common Values of Sine and Cosine
2:46
90 Degrees Undefined
4:36
Slope and Menmonic: ASTC
5:47
Uses of Tangent
5:54
Example: Tangent of Angle is Slope
6:09
7:49
Example 1: Graph Tangent and Cotangent Functions
10:42
Example 2: Tangent and Cotangent of Angles
16:09
Example 3: Odd, Even, or Neither
18:56
Extra Example 1: Tangent and Cotangent of Angles
-1
Extra Example 2: Tangent and Cotangent of Angles
-2
Secant and Cosecant Functions

27m 18s

Intro
0:00
Secant and Cosecant Definitions
0:17
Secant Definition
0:18
Cosecant Definition
0:33
Example 1: Graph Secant Function
0:48
Example 2: Values of Secant and Cosecant
6:49
Example 3: Odd, Even, or Neither
12:49
Extra Example 1: Graph of Cosecant Function
-1
Extra Example 2: Values of Secant and Cosecant
-2
Inverse Trigonometric Functions

32m 58s

Intro
0:00
Arcsine Function
0:24
Restrictions between -1 and 1
0:43
Arcsine Notation
1:26
Arccosine Function
3:07
Restrictions between -1 and 1
3:36
Cosine Notation
3:53
Arctangent Function
4:30
Between -Pi/2 and Pi/2
4:44
Tangent Notation
5:02
Example 1: Domain/Range/Graph of Arcsine
5:45
Example 2: Arcsin/Arccos/Arctan Values
10:46
Example 3: Domain/Range/Graph of Arctangent
17:14
Extra Example 1: Domain/Range/Graph of Arccosine
-1
Extra Example 2: Arcsin/Arccos/Arctan Values
-2
Computations of Inverse Trigonometric Functions

31m 8s

Intro
0:00
Inverse Trigonometric Function Domains and Ranges
0:31
Arcsine
0:41
Arccosine
1:14
Arctangent
1:41
Example 1: Arcsines of Common Values
2:44
Example 2: Odd, Even, or Neither
5:57
Example 3: Arccosines of Common Values
12:24
Extra Example 1: Arctangents of Common Values
-1
Extra Example 2: Arcsin/Arccos/Arctan Values
-2
Section 7: Trigonometric Identities
Pythagorean Identity

19m 11s

Intro
0:00
Pythagorean Identity
0:17
Pythagorean Triangle
0:27
Pythagorean Identity
0:45
Example 1: Use Pythagorean Theorem to Prove Pythagorean Identity
1:14
Example 2: Find Angle Given Cosine and Quadrant
4:18
Example 3: Verify Trigonometric Identity
8:00
Extra Example 1: Use Pythagorean Identity to Prove Pythagorean Theorem
-1
Extra Example 2: Find Angle Given Cosine and Quadrant
-2
Identity Tan(squared)x+1=Sec(squared)x

23m 16s

Intro
0:00
Main Formulas
0:19
Companion to Pythagorean Identity
0:27
For Cotangents and Cosecants
0:52
How to Remember
0:58
Example 1: Prove the Identity
1:40
Example 2: Given Tan Find Sec
3:42
Example 3: Prove the Identity
7:45
Extra Example 1: Prove the Identity
-1
Extra Example 2: Given Sec Find Tan
-2

52m 52s

Intro
0:00
0:09
How to Remember
0:48
Cofunction Identities
1:31
How to Remember Graphically
1:44
Where to Use Cofunction Identities
2:52
Example 1: Derive the Formula for cos(A-B)
3:08
Example 2: Use Addition and Subtraction Formulas
16:03
Example 3: Use Addition and Subtraction Formulas to Prove Identity
25:11
Extra Example 1: Use cos(A-B) and Cofunction Identities
-1
Extra Example 2: Convert to Radians and use Formulas
-2
Double Angle Formulas

29m 5s

Intro
0:00
Main Formula
0:07
How to Remember from Addition Formula
0:18
Two Other Forms
1:35
Example 1: Find Sine and Cosine of Angle using Double Angle
3:16
Example 2: Prove Trigonometric Identity using Double Angle
9:37
Example 3: Use Addition and Subtraction Formulas
12:38
Extra Example 1: Find Sine and Cosine of Angle using Double Angle
-1
Extra Example 2: Prove Trigonometric Identity using Double Angle
-2
Half-Angle Formulas

43m 55s

Intro
0:00
Main Formulas
0:09
Confusing Part
0:34
Example 1: Find Sine and Cosine of Angle using Half-Angle
0:54
Example 2: Prove Trigonometric Identity using Half-Angle
11:51
Example 3: Prove the Half-Angle Formula for Tangents
18:39
Extra Example 1: Find Sine and Cosine of Angle using Half-Angle
-1
Extra Example 2: Prove Trigonometric Identity using Half-Angle
-2
Section 8: Applications of Trigonometry
Trigonometry in Right Angles

25m 43s

Intro
0:00
Master Formula for Right Angles
0:11
SOHCAHTOA
0:15
Only for Right Triangles
1:26
Example 1: Find All Angles in a Triangle
2:19
Example 2: Find Lengths of All Sides of Triangle
7:39
Example 3: Find All Angles in a Triangle
11:00
Extra Example 1: Find All Angles in a Triangle
-1
Extra Example 2: Find Lengths of All Sides of Triangle
-2
Law of Sines

56m 40s

Intro
0:00
Law of Sines Formula
0:18
SOHCAHTOA
0:27
Any Triangle
0:59
Graphical Representation
1:25
Solving Triangle Completely
2:37
When to Use Law of Sines
2:55
ASA, SAA, SSA, AAA
2:59
SAS, SSS for Law of Cosines
7:11
Example 1: How Many Triangles Satisfy Conditions, Solve Completely
8:44
Example 2: How Many Triangles Satisfy Conditions, Solve Completely
15:30
Example 3: How Many Triangles Satisfy Conditions, Solve Completely
28:32
Extra Example 1: How Many Triangles Satisfy Conditions, Solve Completely
-1
Extra Example 2: How Many Triangles Satisfy Conditions, Solve Completely
-2
Law of Cosines

49m 5s

Intro
0:00
Law of Cosines Formula
0:23
Graphical Representation
0:34
Relates Sides to Angles
1:00
Any Triangle
1:20
Generalization of Pythagorean Theorem
1:32
When to Use Law of Cosines
2:26
SAS, SSS
2:30
Heron's Formula
4:49
Semiperimeter S
5:11
Example 1: How Many Triangles Satisfy Conditions, Solve Completely
5:53
Example 2: How Many Triangles Satisfy Conditions, Solve Completely
15:19
Example 3: Find Area of a Triangle Given All Side Lengths
26:33
Extra Example 1: How Many Triangles Satisfy Conditions, Solve Completely
-1
Extra Example 2: Length of Third Side and Area of Triangle
-2
Finding the Area of a Triangle

27m 37s

Intro
0:00
Master Right Triangle Formula and Law of Cosines
0:19
SOHCAHTOA
0:27
Law of Cosines
1:23
Heron's Formula
2:22
Semiperimeter S
2:37
Example 1: Area of Triangle with Two Sides and One Angle
3:12
Example 2: Area of Triangle with Three Sides
6:11
Example 3: Area of Triangle with Three Sides, No Heron's Formula
8:50
Extra Example 1: Area of Triangle with Two Sides and One Angle
-1
Extra Example 2: Area of Triangle with Two Sides and One Angle
-2
Word Problems and Applications of Trigonometry

34m 25s

Intro
0:00
Formulas to Remember
0:11
SOHCAHTOA
0:15
Law of Sines
0:55
Law of Cosines
1:48
Heron's Formula
2:46
Example 1: Telephone Pole Height
4:01
Example 2: Bridge Length
7:48
Example 3: Area of Triangular Field
14:20
Extra Example 1: Kite Height
-1
Extra Example 2: Roads to a Town
-2
Section 9: Systems of Equations and Inequalities
Systems of Linear Equations

55m 40s

Intro
0:00
Introduction
0:04
Graphs as Location of 'True'
1:49
All Locations that Make the Function True
2:25
Understand the Relationship Between Solutions and the Graph
3:43
Systems as Graphs
4:07
Equations as Lines
4:20
Intersection Point
5:19
Three Possibilities for Solutions
6:17
Independent
6:24
Inconsistent
6:36
Dependent
7:06
Solving by Substitution
8:37
Solve for One Variable
9:07
Substitute into the Second Equation
9:34
Solve for Both Variables
10:12
What If a System is Inconsistent or Dependent?
11:08
No Solutions
11:25
Infinite Solutions
12:30
Solving by Elimination
13:56
Example
14:22
Determining the Number of Solutions
16:30
Why Elimination Makes Sense
17:25
Solving by Graphing Calculator
19:59
Systems with More than Two Variables
23:22
Example 1
25:49
Example 2
30:22
Example 3
34:11
Example 4
38:55
Example 5
46:01
(Non-) Example 6
53:37
Systems of Linear Inequalities

1h 13s

Intro
0:00
Introduction
0:04
Inequality Refresher-Solutions
0:46
Equation Solutions vs. Inequality Solutions
1:02
Essentially a Wide Variety of Answers
1:35
Refresher--Negative Multiplication Flips
1:43
Refresher--Negative Flips: Why?
3:19
Multiplication by a Negative
3:43
The Relationship Flips
3:55
Refresher--Stick to Basic Operations
4:34
Linear Equations in Two Variables
6:50
Graphing Linear Inequalities
8:28
Why It Includes a Whole Section
8:43
How to Show The Difference Between Strict and Not Strict Inequalities
10:08
Dashed Line--Not Solutions
11:10
Solid Line--Are Solutions
11:24
11:42
Example of Using a Point
12:41
13:14
Graphing a System
14:53
Set of Solutions is the Overlap
15:17
Example
15:22
Solutions are Best Found Through Graphing
18:05
Linear Programming-Idea
19:52
Use a Linear Objective Function
20:15
Variables in Objective Function have Constraints
21:24
Linear Programming-Method
22:09
Rearrange Equations
22:21
Graph
22:49
Critical Solution is at the Vertex of the Overlap
23:40
Try Each Vertice
24:35
Example 1
24:58
Example 2
28:57
Example 3
33:48
Example 4
43:10
Nonlinear Systems

41m 1s

Intro
0:00
Introduction
0:06
Substitution
1:12
Example
1:22
Elimination
3:46
Example
3:56
Elimination is Less Useful for Nonlinear Systems
4:56
Graphing
5:56
Using a Graphing Calculator
6:44
Number of Solutions
8:44
Systems of Nonlinear Inequalities
10:02
Graph Each Inequality
10:06
Dashed and/or Solid
10:18
11:14
Example 1
13:24
Example 2
15:50
Example 3
22:02
Example 4
29:06
Example 4, cont.
33:40
Section 10: Vectors and Matrices
Vectors

1h 9m 31s

Intro
0:00
Introduction
0:10
Magnitude of the Force
0:22
Direction of the Force
0:48
Vector
0:52
Idea of a Vector
1:30
How Vectors are Denoted
2:00
Component Form
3:20
Angle Brackets and Parentheses
3:50
Magnitude/Length
4:26
Denoting the Magnitude of a Vector
5:16
Direction/Angle
7:52
Always Draw a Picture
8:50
Component Form from Magnitude & Angle
10:10
Scaling by Scalars
14:06
Unit Vectors
16:26
Combining Vectors - Algebraically
18:10
Combining Vectors - Geometrically
19:54
Resultant Vector
20:46
Alternate Component Form: i, j
21:16
The Zero Vector
23:18
Properties of Vectors
24:20
No Multiplication (Between Vectors)
28:30
Dot Product
29:40
Motion in a Medium
30:10
Fish in an Aquarium Example
31:38
More Than Two Dimensions
33:12
More Than Two Dimensions - Magnitude
34:18
Example 1
35:26
Example 2
38:10
Example 3
45:48
Example 4
50:40
Example 4, cont.
56:07
Example 5
1:01:32
Dot Product & Cross Product

35m 20s

Intro
0:00
Introduction
0:08
Dot Product - Definition
0:42
Dot Product Results in a Scalar, Not a Vector
2:10
Example in Two Dimensions
2:34
Angle and the Dot Product
2:58
The Dot Product of Two Vectors is Deeply Related to the Angle Between the Two Vectors
2:59
Proof of Dot Product Formula
4:14
Won't Directly Help Us Better Understand Vectors
4:18
Dot Product - Geometric Interpretation
4:58
We Can Interpret the Dot Product as a Measure of How Long and How Parallel Two Vectors Are
7:26
Dot Product - Perpendicular Vectors
8:24
If the Dot Product of Two Vectors is 0, We Know They are Perpendicular to Each Other
8:54
Cross Product - Definition
11:08
Cross Product Only Works in Three Dimensions
11:09
Cross Product - A Mnemonic
12:16
The Determinant of a 3 x 3 Matrix and Standard Unit Vectors
12:17
Cross Product - Geometric Interpretations
14:30
The Right-Hand Rule
15:17
Cross Product - Geometric Interpretations Cont.
17:00
Example 1
18:40
Example 2
22:50
Example 3
24:04
Example 4
26:20
Bonus Round
29:18
Proof: Dot Product Formula
29:24
Proof: Dot Product Formula, cont.
30:38
Matrices

54m 7s

Intro
0:00
Introduction
0:08
Definition of a Matrix
3:02
Size or Dimension
3:58
Square Matrix
4:42
Denoted by Capital Letters
4:56
When are Two Matrices Equal?
5:04
Examples of Matrices
6:44
Rows x Columns
6:46
7:48
We Use Capitals to Denote a Matrix and Lower Case to Denotes Its Entries
8:32
Using Entries to Talk About Matrices
10:08
Scalar Multiplication
11:26
Scalar = Real Number
11:34
Example
12:36
13:08
Example
14:22
Matrix Multiplication
15:00
Example
18:52
Matrix Multiplication, cont.
19:58
Matrix Multiplication and Order (Size)
25:26
Make Sure Their Orders are Compatible
25:27
Matrix Multiplication is NOT Commutative
28:20
Example
30:08
Special Matrices - Zero Matrix (0)
32:48
Zero Matrix Has 0 for All of its Entries
32:49
Special Matrices - Identity Matrix (I)
34:14
Identity Matrix is a Square Matrix That Has 1 for All Its Entries on the Main Diagonal and 0 for All Other Entries
34:15
Example 1
36:16
Example 2
40:00
Example 3
44:54
Example 4
50:08
Determinants & Inverses of Matrices

47m 12s

Intro
0:00
Introduction
0:06
Not All Matrices Are Invertible
1:30
What Must a Matrix Have to Be Invertible?
2:08
Determinant
2:32
The Determinant is a Real Number Associated With a Square Matrix
2:38
If the Determinant of a Matrix is Nonzero, the Matrix is Invertible
3:40
Determinant of a 2 x 2 Matrix
4:34
Think in Terms of Diagonals
5:12
Minors and Cofactors - Minors
6:24
Example
6:46
Minors and Cofactors - Cofactors
8:00
Cofactor is Closely Based on the Minor
8:01
Alternating Sign Pattern
9:04
Determinant of Larger Matrices
10:56
Example
13:00
Alternative Method for 3x3 Matrices
16:46
Not Recommended
16:48
Inverse of a 2 x 2 Matrix
19:02
Inverse of Larger Matrices
20:00
Using Inverse Matrices
21:06
When Multiplied Together, They Create the Identity Matrix
21:24
Example 1
23:45
Example 2
27:21
Example 3
32:49
Example 4
36:27
Finding the Inverse of Larger Matrices
41:59
General Inverse Method - Step 1
43:25
General Inverse Method - Step 2
43:27
General Inverse Method - Step 2, cont.
43:27
General Inverse Method - Step 3
45:15
Using Matrices to Solve Systems of Linear Equations

58m 34s

Intro
0:00
Introduction
0:12
Augmented Matrix
1:44
We Can Represent the Entire Linear System With an Augmented Matrix
1:50
Row Operations
3:22
Interchange the Locations of Two Rows
3:50
Multiply (or Divide) a Row by a Nonzero Number
3:58
Add (or Subtract) a Multiple of One Row to Another
4:12
Row Operations - Keep Notes!
5:50
Suggested Symbols
7:08
Gauss-Jordan Elimination - Idea
8:04
Gauss-Jordan Elimination - Idea, cont.
9:16
Reduced Row-Echelon Form
9:18
Gauss-Jordan Elimination - Method
11:36
Begin by Writing the System As An Augmented Matrix
11:38
Gauss-Jordan Elimination - Method, cont.
13:48
Cramer's Rule - 2 x 2 Matrices
17:08
Cramer's Rule - n x n Matrices
19:24
Solving with Inverse Matrices
21:10
Solving Inverse Matrices, cont.
25:28
The Mighty (Graphing) Calculator
26:38
Example 1
29:56
Example 2
33:56
Example 3
37:00
Example 3, cont.
45:04
Example 4
51:28
Section 11: Alternate Ways to Graph
Parametric Equations

53m 33s

Intro
0:00
Introduction
0:06
Definition
1:10
Plane Curve
1:24
The Key Idea
2:00
Graphing with Parametric Equations
2:52
Same Graph, Different Equations
5:04
How Is That Possible?
5:36
Same Graph, Different Equations, cont.
5:42
Here's Another to Consider
7:56
Same Plane Curve, But Still Different
8:10
A Metaphor for Parametric Equations
9:36
Think of Parametric Equations As a Way to Describe the Motion of An Object
9:38
Graph Shows Where It Went, But Not Speed
10:32
Eliminating Parameters
12:14
Rectangular Equation
12:16
Caution
13:52
Creating Parametric Equations
14:30
Interesting Graphs
16:38
Graphing Calculators, Yay!
19:18
Example 1
22:36
Example 2
28:26
Example 3
37:36
Example 4
41:00
Projectile Motion
44:26
Example 5
47:00
Polar Coordinates

48m 7s

Intro
0:00
Introduction
0:04
Polar Coordinates Give Us a Way To Describe the Location of a Point
0:26
Polar Equations and Functions
0:50
Plotting Points with Polar Coordinates
1:06
The Distance of the Point from the Origin
1:09
The Angle of the Point
1:33
Give Points as the Ordered Pair (r,θ)
2:03
Visualizing Plotting in Polar Coordinates
2:32
First Way We Can Plot
2:39
Second Way We Can Plot
2:50
First, We'll Look at Visualizing r, Then θ
3:09
Rotate the Length Counter-Clockwise by θ
3:38
Alternatively, We Can Visualize θ, Then r
4:06
'Polar Graph Paper'
6:17
Horizontal and Vertical Tick Marks Are Not Useful for Polar
6:42
Use Concentric Circles to Helps Up See Distance From the Pole
7:08
Can Use Arc Sectors to See Angles
7:57
Multiple Ways to Name a Point
9:17
Examples
9:30
For Any Angle θ, We Can Make an Equivalent Angle
10:44
Negative Values for r
11:58
If r Is Negative, We Go In The Direction Opposite the One That The Angle θ Points Out
12:22
Another Way to Name the Same Point: Add π to θ and Make r Negative
13:44
Converting Between Rectangular and Polar
14:37
Rectangular Way to Name
14:43
Polar Way to Name
14:52
The Rectangular System Must Have a Right Angle Because It's Based on a Rectangle
15:08
Connect Both Systems Through Basic Trigonometry
15:38
Equation to Convert From Polar to Rectangular Coordinate Systems
16:55
Equation to Convert From Rectangular to Polar Coordinate Systems
17:13
Converting to Rectangular is Easy
17:20
Converting to Polar is a Bit Trickier
17:21
Draw Pictures
18:55
Example 1
19:50
Example 2
25:17
Example 3
31:05
Example 4
35:56
Example 5
41:49
Polar Equations & Functions

38m 16s

Intro
0:00
Introduction
0:04
Equations and Functions
1:16
Independent Variable
1:21
Dependent Variable
1:30
Examples
1:46
Always Assume That θ Is In Radians
2:44
Graphing in Polar Coordinates
3:29
Graph is the Same Way We Graph 'Normal' Stuff
3:32
Example
3:52
Graphing in Polar - Example, Cont.
6:45
Tips for Graphing
9:23
Notice Patterns
10:19
Repetition
13:39
Graphing Equations of One Variable
14:39
Converting Coordinate Types
16:16
Use the Same Conversion Formulas From the Previous Lesson
16:23
Interesting Graphs
17:48
Example 1
18:03
Example 2
18:34
Graphing Calculators, Yay!
19:07
Plot Random Things, Alter Equations You Understand, Get a Sense for How Polar Stuff Works
19:11
Check Out the Appendix
19:26
Example 1
21:36
Example 2
28:13
Example 3
34:24
Example 4
35:52
Section 12: Complex Numbers and Polar Coordinates
Polar Form of Complex Numbers

40m 43s

Intro
0:00
Polar Coordinates
0:49
Rectangular Form
0:52
Polar Form
1:25
R and Theta
1:51
Polar Form Conversion
2:27
R and Theta
2:35
Optimal Values
4:05
Euler's Formula
4:25
Multiplying Two Complex Numbers in Polar Form
6:10
Multiply r's Together and Add Exponents
6:32
Example 1: Convert Rectangular to Polar Form
7:17
Example 2: Convert Polar to Rectangular Form
13:49
Example 3: Multiply Two Complex Numbers
17:28
Extra Example 1: Convert Between Rectangular and Polar Forms
-1
Extra Example 2: Simplify Expression to Polar Form
-2
DeMoivre's Theorem

57m 37s

Intro
0:00
Introduction to DeMoivre's Theorem
0:10
n nth Roots
3:06
DeMoivre's Theorem: Finding nth Roots
3:52
Relation to Unit Circle
6:29
One nth Root for Each Value of k
7:11
Example 1: Convert to Polar Form and Use DeMoivre's Theorem
8:24
Example 2: Find Complex Eighth Roots
15:27
Example 3: Find Complex Roots
27:49
Extra Example 1: Convert to Polar Form and Use DeMoivre's Theorem
-1
Extra Example 2: Find Complex Fourth Roots
-2
Section 13: Counting & Probability
Counting

31m 36s

Intro
0:00
Introduction
0:08
Combinatorics
0:56
Definition: Event
1:24
Example
1:50
Visualizing an Event
3:02
Branching line diagram
3:06
3:40
Example
4:18
Multiplication Principle
5:42
Example
6:24
Pigeonhole Principle
8:06
Example
10:26
Draw Pictures
11:06
Example 1
12:02
Example 2
14:16
Example 3
17:34
Example 4
21:26
Example 5
25:14
Permutations & Combinations

44m 3s

Intro
0:00
Introduction
0:08
Permutation
0:42
Combination
1:10
Towards a Permutation Formula
2:38
How Many Ways Can We Arrange the Letters A, B, C, D, and E?
3:02
Towards a Permutation Formula, cont.
3:34
Factorial Notation
6:56
Symbol Is '!'
6:58
Examples
7:32
Permutation of n Objects
8:44
Permutation of r Objects out of n
9:04
What If We Have More Objects Than We Have Slots to Fit Them Into?
9:46
Permutation of r Objects Out of n, cont.
10:28
Distinguishable Permutations
14:46
What If Not All Of the Objects We're Permuting Are Distinguishable From Each Other?
14:48
Distinguishable Permutations, cont.
17:04
Combinations
19:04
Combinations, cont.
20:56
Example 1
23:10
Example 2
26:16
Example 3
28:28
Example 4
31:52
Example 5
33:58
Example 6
36:34
Probability

36m 58s

Intro
0:00
Introduction
0:06
Definition: Sample Space
1:18
Event = Something Happening
1:20
Sample Space
1:36
Probability of an Event
2:12
Let E Be An Event and S Be The Corresponding Sample Space
2:14
'Equally Likely' Is Important
3:52
Fair and Random
5:26
Interpreting Probability
6:34
How Can We Interpret This Value?
7:24
We Can Represent Probability As a Fraction, a Decimal, Or a Percentage
8:04
One of Multiple Events Occurring
9:52
Mutually Exclusive Events
10:38
What If The Events Are Not Mutually Exclusive?
12:20
Taking the Possibility of Overlap Into Account
13:24
An Event Not Occurring
17:14
Complement of E
17:22
Independent Events
19:36
Independent
19:48
Conditional Events
21:28
What Is The Events Are Not Independent Though?
21:30
Conditional Probability
22:16
Conditional Events, cont.
23:51
Example 1
25:27
Example 2
27:09
Example 3
28:57
Example 4
30:51
Example 5
34:15
Section 14: Conic Sections
Parabolas

41m 27s

Intro
0:00
What is a Parabola?
0:20
Definition of a Parabola
0:29
Focus
0:59
Directrix
1:15
Axis of Symmetry
3:08
Vertex
3:33
Minimum or Maximum
3:44
Standard Form
4:59
Horizontal Parabolas
5:08
Vertex Form
5:19
Upward or Downward
5:41
Example: Standard Form
6:06
Graphing Parabolas
8:31
Shifting
8:51
Example: Completing the Square
9:22
Symmetry and Translation
12:18
Example: Graph Parabola
12:40
Latus Rectum
17:13
Length
18:15
Example: Latus Rectum
18:35
Horizontal Parabolas
18:57
Not Functions
20:08
Example: Horizontal Parabola
21:21
Focus and Directrix
24:11
Horizontal
24:48
Example 1: Parabola Standard Form
25:12
Example 2: Graph Parabola
30:00
Example 3: Graph Parabola
33:13
Example 4: Parabola Equation
37:28
Circles

21m 3s

Intro
0:00
What are Circles?
0:08
Example: Equidistant
0:17
0:32
Equation of a Circle
0:44
Example: Standard Form
1:11
Graphing Circles
1:47
Example: Circle
1:56
Center Not at Origin
3:07
Example: Completing the Square
3:51
Example 1: Equation of Circle
6:44
11:51
15:08
Example 4: Equation of Circle
16:57
Ellipses

46m 51s

Intro
0:00
What Are Ellipses?
0:11
Foci
0:23
Properties of Ellipses
1:43
Major Axis, Minor Axis
1:47
Center
1:54
Length of Major Axis and Minor Axis
3:21
Standard Form
5:33
Example: Standard Form of Ellipse
6:09
Vertical Major Axis
9:14
Example: Vertical Major Axis
9:46
Graphing Ellipses
12:51
Complete the Square and Symmetry
13:00
Example: Graphing Ellipse
13:16
Equation with Center at (h, k)
19:57
Horizontal and Vertical
20:14
Difference
20:27
Example: Center at (h, k)
20:55
Example 1: Equation of Ellipse
24:05
Example 2: Equation of Ellipse
27:57
Example 3: Equation of Ellipse
32:32
Example 4: Graph Ellipse
38:27
Hyperbolas

38m 15s

Intro
0:00
What are Hyperbolas?
0:12
Two Branches
0:18
Foci
0:38
Properties
2:00
Transverse Axis and Conjugate Axis
2:06
Vertices
2:46
Length of Transverse Axis
3:14
Distance Between Foci
3:31
Length of Conjugate Axis
3:38
Standard Form
5:45
Vertex Location
6:36
Known Points
6:52
Vertical Transverse Axis
7:26
Vertex Location
7:50
Asymptotes
8:36
Vertex Location
8:56
Rectangle
9:28
Diagonals
10:29
Graphing Hyperbolas
12:58
Example: Hyperbola
13:16
Equation with Center at (h, k)
16:32
Example: Center at (h, k)
17:21
Example 1: Equation of Hyperbola
19:20
Example 2: Equation of Hyperbola
22:48
Example 3: Graph Hyperbola
26:05
Example 4: Equation of Hyperbola
36:29
Conic Sections

18m 43s

Intro
0:00
Conic Sections
0:16
Double Cone Sections
0:24
Standard Form
1:27
General Form
1:37
Identify Conic Sections
2:16
B = 0
2:50
X and Y
3:22
Identify Conic Sections, Cont.
4:46
Parabola
5:17
Circle
5:51
Ellipse
6:31
Hyperbola
7:10
Example 1: Identify Conic Section
8:01
Example 2: Identify Conic Section
11:03
Example 3: Identify Conic Section
11:38
Example 4: Identify Conic Section
14:50
Section 15: Sequences, Series, & Induction
Introduction to Sequences

57m 45s

Intro
0:00
Introduction
0:06
Definition: Sequence
0:28
Infinite Sequence
2:08
Finite Sequence
2:22
Length
2:58
Formula for the nth Term
3:22
Defining a Sequence Recursively
5:54
Initial Term
7:58
Sequences and Patterns
10:40
First, Identify a Pattern
12:52
How to Get From One Term to the Next
17:38
Tips for Finding Patterns
19:52
More Tips for Finding Patterns
24:14
Even More Tips
26:50
Example 1
30:32
Example 2
34:54
Fibonacci Sequence
34:55
Example 3
38:40
Example 4
45:02
Example 5
49:26
Example 6
51:54
Introduction to Series

40m 27s

Intro
0:00
Introduction
0:06
Definition: Series
1:20
Why We Need Notation
2:48
Simga Notation (AKA Summation Notation)
4:44
Thing Being Summed
5:42
Index of Summation
6:21
Lower Limit of Summation
7:09
Upper Limit of Summation
7:23
Sigma Notation, Example
7:36
Sigma Notation for Infinite Series
9:08
How to Reindex
10:58
How to Reindex, Expanding
12:56
How to Reindex, Substitution
16:46
Properties of Sums
19:42
Example 1
23:46
Example 2
25:34
Example 3
27:12
Example 4
29:54
Example 5
32:06
Example 6
37:16
Arithmetic Sequences & Series

31m 36s

Intro
0:00
Introduction
0:05
Definition: Arithmetic Sequence
0:47
Common Difference
1:13
Two Examples
1:19
Form for the nth Term
2:14
Recursive Relation
2:33
Towards an Arithmetic Series Formula
5:12
Creating a General Formula
10:09
General Formula for Arithmetic Series
14:23
Example 1
15:46
Example 2
17:37
Example 3
22:21
Example 4
24:09
Example 5
27:14
Geometric Sequences & Series

39m 27s

Intro
0:00
Introduction
0:06
Definition
0:48
Form for the nth Term
2:42
Formula for Geometric Series
5:16
Infinite Geometric Series
11:48
Diverges
13:04
Converges
14:48
Formula for Infinite Geometric Series
16:32
Example 1
20:32
Example 2
22:02
Example 3
26:00
Example 4
30:48
Example 5
34:28
Mathematical Induction

49m 53s

Intro
0:00
Introduction
0:06
Belief Vs. Proof
1:22
A Metaphor for Induction
6:14
The Principle of Mathematical Induction
11:38
Base Case
13:24
Inductive Step
13:30
Inductive Hypothesis
13:52
A Remark on Statements
14:18
Using Mathematical Induction
16:58
Working Example
19:58
Finding Patterns
28:46
Example 1
30:17
Example 2
37:50
Example 3
42:38
The Binomial Theorem

1h 13m 13s

Intro
0:00
Introduction
0:06
We've Learned That a Binomial Is An Expression That Has Two Terms
0:07
Understanding Binomial Coefficients
1:20
Things We Notice
2:24
What Goes In the Blanks?
5:52
Each Blank is Called a Binomial Coefficient
6:18
The Binomial Theorem
6:38
Example
8:10
The Binomial Theorem, cont.
10:46
We Can Also Write This Expression Compactly Using Sigma Notation
12:06
Proof of the Binomial Theorem
13:22
Proving the Binomial Theorem Is Within Our Reach
13:24
Pascal's Triangle
15:12
Pascal's Triangle, cont.
16:12
16:24
Zeroth Row
18:04
First Row
18:12
Why Do We Care About Pascal's Triangle?
18:50
Pascal's Triangle, Example
19:26
Example 1
21:26
Example 2
24:34
Example 3
28:34
Example 4
32:28
Example 5
37:12
Time for the Fireworks!
43:38
Proof of the Binomial Theorem
43:44
We'll Prove This By Induction
44:04
Proof (By Induction)
46:36
Proof, Base Case
47:00
Proof, Inductive Step - Notation Discussion
49:22
Induction Step
49:24
Proof, Inductive Step - Setting Up
52:26
Induction Hypothesis
52:34
What We What To Show
52:44
Proof, Inductive Step - Start
54:18
Proof, Inductive Step - Middle
55:38
Expand Sigma Notations
55:48
Proof, Inductive Step - Middle, cont.
58:40
Proof, Inductive Step - Checking In
1:01:08
Let's Check In With Our Original Goal
1:01:12
Want to Show
1:01:18
Lemma - A Mini Theorem
1:02:18
Proof, Inductive Step - Lemma
1:02:52
Proof of Lemma: Let's Investigate the Left Side
1:03:08
Proof, Inductive Step - Nearly There
1:07:54
Proof, Inductive Step - End!
1:09:18
Proof, Inductive Step - End!, cont.
1:11:01
Section 16: Preview of Calculus
Idea of a Limit

40m 22s

Intro
0:00
Introduction
0:05
Motivating Example
1:26
Fuzzy Notion of a Limit
3:38
Limit is the Vertical Location a Function is Headed Towards
3:44
Limit is What the Function Output is Going to Be
4:15
Limit Notation
4:33
Exploring Limits - 'Ordinary' Function
5:26
Test Out
5:27
Graphing, We See The Answer Is What We Would Expect
5:44
Exploring Limits - Piecewise Function
6:45
If We Modify the Function a Bit
6:49
Exploring Limits - A Visual Conception
10:08
Definition of a Limit
12:07
If f(x) Becomes Arbitrarily Close to Some Number L as x Approaches Some Number c, Then the Limit of f(x) As a Approaches c is L.
12:09
We Are Not Concerned with f(x) at x=c
12:49
We Are Considering x Approaching From All Directions, Not Just One Side
13:10
Limits Do Not Always Exist
15:47
Finding Limits
19:49
Graphs
19:52
Tables
21:48
Precise Methods
24:53
Example 1
26:06
Example 2
27:39
Example 3
30:51
Example 4
33:11
Example 5
37:07
Formal Definition of a Limit

57m 11s

Intro
0:00
Introduction
0:06
New Greek Letters
2:42
Delta
3:14
Epsilon
3:46
Sometimes Called the Epsilon-Delta Definition of a Limit
3:56
Formal Definition of a Limit
4:22
What does it MEAN!?!?
5:00
The Groundwork
5:38
Set Up the Limit
5:39
The Function is Defined Over Some Portion of the Reals
5:58
The Horizontal Location is the Value the Limit Will Approach
6:28
The Vertical Location L is Where the Limit Goes To
7:00
The Epsilon-Delta Part
7:26
The Hard Part is the Second Part of the Definition
7:30
Second Half of Definition
10:04
Restrictions on the Allowed x Values
10:28
The Epsilon-Delta Part, cont.
13:34
Sherlock Holmes and Dr. Watson
15:08
The Adventure of the Delta-Epsilon Limit
15:16
Setting
15:18
We Begin By Setting Up the Game As Follows
15:52
The Adventure of the Delta-Epsilon, cont.
17:24
17:46
What If I Try Larger?
19:39
Technically, You Haven't Proven the Limit
20:53
Here is the Method
21:18
What We Should Concern Ourselves With
22:20
Investigate the Left Sides of the Expressions
25:24
We Can Create the Following Inequalities
28:08
Finally…
28:50
Nothing Like a Good Proof to Develop the Appetite
30:42
Example 1
31:02
Example 1, cont.
36:26
Example 2
41:46
Example 2, cont.
47:50
Finding Limits

32m 40s

Intro
0:00
Introduction
0:08
Method - 'Normal' Functions
2:04
The Easiest Limits to Find
2:06
It Does Not 'Break'
2:18
It Is Not Piecewise
2:26
Method - 'Normal' Functions, Example
3:38
Method - 'Normal' Functions, cont.
4:54
The Functions We're Used to Working With Go Where We Expect Them To Go
5:22
5:42
Method - Canceling Factors
7:18
One Weird Thing That Often Happens is Dividing By 0
7:26
Method - Canceling Factors, cont.
8:16
Notice That The Two Functions Are Identical With the Exception of x=0
8:20
Method - Canceling Factors, cont.
10:00
Example
10:52
Method - Rationalization
12:04
Rationalizing a Portion of Some Fraction
12:05
Conjugate
12:26
Method - Rationalization, cont.
13:14
Example
13:50
Method - Piecewise
16:28
The Limits of Piecewise Functions
16:30
Example 1
17:42
Example 2
18:44
Example 3
20:20
Example 4
22:24
Example 5
24:24
Example 6
27:12
Continuity & One-Sided Limits

32m 43s

Intro
0:00
Introduction
0:06
Motivating Example
0:56
Continuity - Idea
2:14
Continuous Function
2:18
All Parts of Function Are Connected
2:28
Function's Graph Can Be Drawn Without Lifting Pencil
2:36
There Are No Breaks or Holes in Graph
2:56
Continuity - Idea, cont.
3:38
We Can Interpret the Break in the Continuity of f(x) as an Issue With the Function 'Jumping'
3:52
Continuity - Definition
5:16
A Break in Continuity is Caused By the Limit Not Matching Up With What the Function Does
5:18
Discontinuous
6:02
Discontinuity
6:10
Continuity and 'Normal' Functions
6:48
Return of the Motivating Example
8:14
One-Sided Limit
8:48
One-Sided Limit - Definition
9:16
Only Considers One Side
9:20
Be Careful to Keep Track of Which Symbol Goes With Which Side
10:06
One-Sided Limit - Example
10:50
There Does Not Necessarily Need to Be a Connection Between Left or Right Side Limits
11:16
Normal Limits and One-Sided Limits
12:08
Limits of Piecewise Functions
14:12
'Breakover' Points
14:22
We Find the Limit of a Piecewise Function By Checking If the Left and Right Side Limits Agree With Each Other
15:34
Example 1
16:40
Example 2
18:54
Example 3
22:00
Example 4
26:36
Limits at Infinity & Limits of Sequences

32m 49s

Intro
0:00
Introduction
0:06
Definition: Limit of a Function at Infinity
1:44
A Limit at Infinity Works Very Similarly to How a Normal Limit Works
2:38
Evaluating Limits at Infinity
4:08
Rational Functions
4:17
Examples
4:30
For a Rational Function, the Question Boils Down to Comparing the Long Term Growth Rates of the Numerator and Denominator
5:22
There are Three Possibilities
6:36
Evaluating Limits at Infinity, cont.
8:08
Does the Function Grow Without Bound? Will It 'Settle Down' Over Time?
10:06
10:26
Limit of a Sequence
12:20
What Value Does the Sequence Tend to Do in the Long-Run?
12:41
The Limit of a Sequence is Very Similar to the Limit of a Function at Infinity
12:52
Numerical Evaluation
14:16
Numerically: Plug in Numbers and See What Comes Out
14:24
Example 1
16:42
Example 2
21:00
Example 3
22:08
Example 4
26:14
Example 5
28:10
Example 6
31:06
Instantaneous Slope & Tangents (Derivatives)

51m 13s

Intro
0:00
Introduction
0:08
The Derivative of a Function Gives Us a Way to Talk About 'How Fast' the Function If Changing
0:16
Instantaneous Slop
0:22
Instantaneous Rate of Change
0:28
Slope
1:24
The Vertical Change Divided by the Horizontal
1:40
Idea of Instantaneous Slope
2:10
What If We Wanted to Apply the Idea of Slope to a Non-Line?
2:14
Tangent to a Circle
3:52
What is the Tangent Line for a Circle?
4:42
Tangent to a Curve
5:20
Towards a Derivative - Average Slope
6:36
Towards a Derivative - Average Slope, cont.
8:20
An Approximation
11:24
Towards a Derivative - General Form
13:18
Towards a Derivative - General Form, cont.
16:46
An h Grows Smaller, Our Slope Approximation Becomes Better
18:44
Towards a Derivative - Limits!
20:04
Towards a Derivative - Limits!, cont.
22:08
We Want to Show the Slope at x=1
22:34
Towards a Derivative - Checking Our Slope
23:12
Definition of the Derivative
23:54
Derivative: A Way to Find the Instantaneous Slope of a Function at Any Point
23:58
Differentiation
24:54
Notation for the Derivative
25:58
The Derivative is a Very Important Idea In Calculus
26:04
The Important Idea
27:34
Why Did We Learn the Formal Definition to Find a Derivative?
28:18
Example 1
30:50
Example 2
36:06
Example 3
40:24
The Power Rule
44:16
Makes It Easier to Find the Derivative of a Function
44:24
Examples
45:04
n Is Any Constant Number
45:46
Example 4
46:26
Area Under a Curve (Integrals)

45m 26s

Intro
0:00
Introduction
0:06
Integral
0:12
Idea of Area Under a Curve
1:18
Approximation by Rectangles
2:12
The Easiest Way to Find Area is With a Rectangle
2:18
Various Methods for Choosing Rectangles
4:30
Rectangle Method - Left-Most Point
5:12
The Left-Most Point
5:16
Rectangle Method - Right-Most Point
5:58
The Right-Most Point
6:00
Rectangle Method - Mid-Point
6:42
Horizontal Mid-Point
6:48
Rectangle Method - Maximum (Upper Sum)
7:34
Maximum Height
7:40
Rectangle Method - Minimum
8:54
Minimum Height
9:02
Evaluating the Area Approximation
10:08
Split the Interval Into n Sub-Intervals
10:30
More Rectangles, Better Approximation
12:14
The More We Us , the Better Our Approximation Becomes
12:16
Our Approximation Becomes More Accurate as the Number of Rectangles n Goes Off to Infinity
12:44
Finding Area with a Limit
13:08
If This Limit Exists, It Is Called the Integral From a to b
14:08
The Process of Finding Integrals is Called Integration
14:22
The Big Reveal
14:40
The Integral is Based on the Antiderivative
14:46
The Big Reveal - Wait, Why?
16:28
The Rate of Change for the Area is Based on the Height of the Function
16:50
Height is the Derivative of Area, So Area is Based on the Antiderivative of Height
17:50
Example 1
19:06
Example 2
22:48
Example 3
29:06
Example 3, cont.
35:14
Example 4
40:14
Section 17: Appendix: Graphing Calculators

10m 41s

Intro
0:00
0:06
Should I Get a Graphing Utility?
0:20
Free Graphing Utilities - Web Based
0:38
Personal Favorite: Desmos
0:58
Free Graphing Utilities - Offline Programs
1:18
GeoGebra
1:31
Microsoft Mathematics
1:50
Grapher
2:18
Other Graphing Utilities - Tablet/Phone
2:48
Should You Buy a Graphing Calculator?
3:22
The Only Real Downside
4:10
4:20
If You Plan on Continuing in Math and/or Science
4:26
If Money is Not Particularly Tight for You
4:32
If You Don't Plan to Continue in Math and Science
5:02
If You Do Plan to Continue and Money Is Tight
5:28
5:44
Which Graphing Calculator is Best?
5:46
Too Many Factors
5:54
6:12
The Old Standby
7:10
TI-83 (Plus)
7:16
TI-84 (Plus)
7:18
9:17
9:19
9:35
10:09
Graphing Calculator Basics

10m 51s

Intro
0:00
0:06
Skim It
0:20
Play Around and Experiment
0:34
Syntax
0:40
Definition of Syntax in English and Math
0:46
Pay Careful Attention to Your Syntax When Working With a Calculator
2:08
Make Sure You Use Parentheses to Indicate the Proper Order of Operations
2:16
3:54
Settings
4:58
You'll Almost Never Need to Change the Settings on Your Calculator
5:00
Tell Calculator In Settings Whether the Angles Are In Radians or Degrees
5:26
Graphing Mode
6:32
Error Messages
7:10
Don't Panic
7:11
Internet Search
7:32
So Many Things
8:14
More Powerful Than You Realize
8:18
Other Things Your Graphing Calculator Can Do
8:24
Playing Around
9:16
Graphing Functions, Window Settings, & Table of Values

10m 38s

Intro
0:00
Graphing Functions
0:18
Graphing Calculator Expects the Variable to Be x
0:28
Syntax
0:58
The Syntax We Choose Will Affect How the Function Graphs
1:00
Use Parentheses
1:26
The Viewing Window
2:00
One of the Most Important Ideas When Graphing Is To Think About The Viewing Window
2:01
For Example
2:30
The Viewing Window, cont.
2:36
Window Settings
3:24
Manually Choose Window Settings
4:20
x Min
4:40
x Max
4:42
y Min
4:44
y Max
4:46
Changing the x Scale or y Scale
5:08
Window Settings, cont.
5:44
Table of Values
7:38
Allows You to Quickly Churn Out Values for Various Inputs
7:42
For example
7:44
Changing the Independent Variable From 'Automatic' to 'Ask'
8:50
Finding Points of Interest

9m 45s

Intro
0:00
Points of Interest
0:06
Interesting Points on the Graph
0:11
Roots/Zeros (Zero)
0:18
Relative Minimums (Min)
0:26
Relative Maximums (Max)
0:32
Intersections (Intersection)
0:38
Finding Points of Interest - Process
1:48
Graph the Function
1:49
2:12
Choose Point of Interest Type
2:54
Identify Where Search Should Occur
3:04
Give a Guess
3:36
Get Result
4:06
5:10
Find Out What Input Value Causes a Certain Output
5:12
For Example
5:24
7:18
Derivative
7:22
Integral
7:30
But How Do You Show Work?
8:20
Parametric & Polar Graphs

7m 8s

Intro
0:00
Change Graph Type
0:08
Located in General 'Settings'
0:16
Graphing in Parametric
1:06
Set Up Both Horizontal Function and Vertical Function
1:08
For Example
2:04
Graphing in Polar
4:00
For Example
4:28
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• ## Related Books 1 answer Last reply by: Professor Selhorst-JonesSun May 10, 2020 11:50 PMPost by Chessdongdong on May 10, 2020How does 6y = -3x + 9 turn into y = -3/2 x + 3? This is at approximately 7:30 into the lecture

### Nonlinear Systems

• A system of equations does not necessarily have to be linear (made up of straight lines only). Nonetheless, we can still use the methods we learned about in previous lessons.
• Substitution is the most fundamental way to solve any system of equations: put one variable in terms of the other(s), then substitute and work to a solution.
• In elimination, we add a multiple of one equation to the other to eliminate variables. In general, elimination is less useful for nonlinear systems. While it still works, it can be difficult to eliminate variables because the equations aren't linear, so they don't match up as easily for cancellation.
• We can also graph each equation in the system: wherever they intersect is a solution to the system. If you have a graphing calculator, you can use that to find the points of intersection for the system. [However, you will have to first put the equations into a form that you can enter into your graphing calculator: y = .]
• Unlike a linear system of equations, there can be any number of solutions. The only way to figure out how many solutions there are is by solving the system.
• Working with nonlinear inequalities is very similar to working with linear inequalities:
• Graph each inequality (as if they were equations);
• Dashed   < ,   > ;        Solid:   ≤ ,   ≥ ;
• Shade appropriately (use test points to help).

### Nonlinear Systems

Find the solution(s) to the system (if possible).
 y = x+5               y=x2 + x −4
• Solve by substitution. For this problem, the equations are already in the form y=stuff, so we can just set those portions equal and solve for x:
 x+5 = x2 + x −4
• Solving for x, we see that we're working with a polynomial equation, so get everything on one side and a 0 on the other:
 x+5 = x2 + x −4     ⇒     0 = x2 − 9
Factor to find the solutions for x:
 0 = x2 − 9     ⇒     0 = (x+3)(x−3)
Thus, we have two possible values: x=−3 and x=3.
• Before we're done, we need to find the y-value that matches with each of those. x=−3:
 y = x+5     ⇒     y = (−3) + 5     =     2
x=3:
 y = x+5     ⇒     y = (3) +5     =     8
(−3,  2) and (3,  8)
Find the solution(s) to the system (if possible).
 y = x2 − 3x + 5               y = −x3 −x2 + 5x + 5
• Solve by substitution. For this problem, the equations are already in the form y=stuff, so we can just set those portions equal and solve for x:
 x2 − 3x + 5 = −x3 −x2 + 5x + 5
• Solving for x, we see that we're working with a polynomial equation, so get everything on one side and a 0 on the other:
 x2 − 3x + 5 = −x3 −x2 + 5x + 5     ⇒     0 = −x3 − 2x2 + 8x
Factor to find the solutions for x:
 0 = −x3 − 2x2 + 8x     ⇒     0 = −x(x2+2x−8)     ⇒     0 = −x(x+4)(x−2)
Thus, we have three possible values: x=−4, x=0, and x=2.
• Before we're done, we need to find the y-value that matches with each of those. x=−4:
 y = x2 − 3x + 5     ⇒     y = (−4)2 −3(−4)+5     =     33
x=0:
 y = x2 − 3x + 5     ⇒     y = (0)2 −3(0)+5     =     5
x=2:
 y = x2 − 3x + 5     ⇒     y = (2)2 −3(2)+5     =     3
(−4, 33),   (0,  5),  and  (2,  3)
Find the solution(s) to the system (if possible).
 xy = 4               3x−2y = 5
• Solve by substitution. Solve for y in the first equation so we can plug it in to the second:
 xy = 4     ⇒     y = 4 x
Now we can plug into the second equation:
 3x − 2 ⎛⎝ 4 x ⎞⎠ = 5
• It will be easier to not have a variable in the denominator of a fraction, so multiply both sides by x:
 3x − 8 x = 5     ⇒     3x2 − 8 = 5x
We now see we're working to solve a polynomial equation, so get everything on one side:
 3x2 − 8 = 5x     ⇒     3x2 − 5x − 8 = 0
• This looks rather difficult to factor, so let's use the quadratic formula:
x = −b ± √ b2 − 4ac

2a
⇒     −(−5) ± √ (−5)2 − 4(3)(−8)

2(3)
Simplify:
x = 5 ± √ 25 +96

6
=     5 ± √ 121

6
=     5 ±11

6
Thus, we have two solutions:
 x = 5+11 6 = 8 3 and        x = 5−11 6 = −1
• Before we're done, we need to find the y-value that matches with each of those. x=[8/3]:
 xy = 4     ⇒ ⎛⎝ 8 3 ⎞⎠ y = 4     ⇒     y = 4 · 3 8 ⇒     y = 3 2
x = −1:
 xy = 4     ⇒     (−1) y = 4     ⇒     y = −4
( [8/3],  [3/2] ),    (−1, −4)
Find the solution(s) to the system (if possible):
 z = x2 + y2               z−x−y=0               z = 4y
• Do not let yourself be worried that there are three variables instead of just two: we still approach it in the same manner-solve for a variable in terms of the others, plug in, repeat until you have an equation with just one variable.
• We can approach this by working through the variables in any order, but it looks easiest to plug the last equation (z=4y) into the middle equation:
 z−x−y=0     ⇒     (4y) − x − y = 0     ⇒     3y − x = 0     ⇒     3y = x
We often tend to solve for y in terms of x, but for this problem, it's better to put everything in terms of y because we started with z in terms of y. [Although you could do it a different way, if you wanted.] We now have x = 3y and z=4y.
• We can now plug these in to our first equation:
 z = x2 + y2     ⇒     (4y) = (3y)2 + y2     ⇒     4y = 9y2 + y2     ⇒     4y = 10y2
We see we're working with a polynomial equation, so get everything on one side and factor:
 4y = 10y2     ⇒     0 = 10y2 − 4y     ⇒     0 = y (10y−4)
Which gives solutions of y=0 and y = [2/5].
• Before we're done, we need to find the x-value and z-value that matches with each of those. y=0:
 x=3y    =   3(0)    =   0 ⎢⎢ z=4y    =   4(0)    =   0
y=[2/5]:
 x = 3y    =   3 ⎛⎝ 2 5 ⎞⎠ = 6 5 ⎢⎢ z = 4y    =   4 ⎛⎝ 2 5 ⎞⎠ = 8 5
(0,  0,  0),     ([6/5],  [2/5],  [8/5] )
Using a graphing calculator, numerically solve for the solution(s) to the system below (if possible). Give your answer to two decimal places.
 x2 + y2 = 25               4 sin(x+3.5) + 2
[The argument of the trig function should be in radians, so make sure your calculator is in that mode.]
• If we tried to solve this using substitution and algebra, we would find that the problem would become extremely difficult. However, we can get a good approximation of the precise answer by using a graphing calculator. To do this, our first step is to get both of the equations into a format we can graph. That is, something in the form y=stuff.
• The second equation is easy, because it's already in the desired form. The first equation isn't too difficult, but it requires us to catch a little trick. Notice, if we worked to solve for y in the first equation (so we could graph it), we would do the following:
 x2 + y2 = 25     ⇒     y2 = 25−x2
Next, we would need to take the square root of both sides. However!, we must remember that when we take the square root of both sides in algebra, we must put a ± symbol in. If we forget this, we will only get the positive, top half of the graph for the first equation. Thus, we get y = ±√{25−x2}. So in the end, our first equation splits into two for graphing on a calculator:
x2 + y2 = 25     ⇒
 y
 =
 √ 25−x2
 y
 =
 − √ 25−x2
• Plug in both of the "split" versions into your graphing calculator along with the second equation from the system and you should get a graph something along the lines of the below. [If your graph looks very different, make sure your graphing calculator is in radians mode and that you entered everything correctly.] • From the graph, we see that we have a total of four intersections, so there are a total of four solutions to the system of equations. Using your graphing calculator, select the 'intersection' command (if you've never done this before, check out the Appendix to this course on graphing calculators), then select the two functions involved and the interval where the calculator should search for an intersection. Notice that the top half and the bottom half of the circle are treated as two different functions from the calculator's point of view. That means you have to make sure to choose the appropriate half of the circle (along with the trig function) when looking for an intersection point.
(−4.69, −1.72),    (−2.97, 4.02),    (−1.16, 4.86),    (3.25, 3.80)
Graph the set of solutions to the system below.
 y ≤ 2x−3               y > x2−5
• It usually helps to begin by putting the inequalities in a format that is easy to graph, like one where y is alone on one side. Both of the inequalities are already in such a form, so we can immediately plot them.
• Plot out a line or curve based on each inequality. While plotting, treat it as if it were a normal equation that you were graphing. The only thing to keep in mind is that ≤ and ≥ get solid lines, while the strict inequalities of < and > get dashed lines.
• Once every line/curve is plotted on the graph, (and solid or dashed, according to the inequality type), shade each one according to its inequality. This can be done in one of two ways. First, if it's structured to have y alone on one side (like ours are), you can look at the "direction" of the inequality sign. If the y is greater (y ≥ or y > ), then we shade above the line. If the y is lesser (y ≤ or y < ), then we shade below the line. Alternatively, if you're not sure of the above or the inequality is not in slope-intercept, choose a "test point" on the graph. Plug it in to the inequality. If it works, shade the side that the test point is on. If it does not satisfy the inequality (it "breaks"), shade the opposite side.
• Once you have shaded each of the inequalities, look for where the shadings overlap. The overlap is the set of solutions. Graph the set of solutions to the system below.
 y > 2x−5               y ≤ 3x+1 +1
• It usually helps to begin by putting the inequalities in a format that is easy to graph, like one where y is alone on one side. Both of the inequalities are already in such a form, so we can immediately plot them.
• Plot out a line or curve based on each inequality. While plotting, treat it as if it were a normal equation that you were graphing. The only thing to keep in mind is that ≤ and ≥ get solid lines, while the strict inequalities of < and > get dashed lines.
• Once every line/curve is plotted on the graph, (and solid or dashed, according to the inequality type), shade each one according to its inequality. This can be done in one of two ways. First, if it's structured to have y alone on one side (like ours are), you can look at the "direction" of the inequality sign. If the y is greater (y ≥ or y > ), then we shade above the line. If the y is lesser (y ≤ or y < ), then we shade below the line. Alternatively, if you're not sure of the above or the inequality is not in slope-intercept, choose a "test point" on the graph. Plug it in to the inequality. If it works, shade the side that the test point is on. If it does not satisfy the inequality (it "breaks"), shade the opposite side.
• Once you have shaded each of the inequalities, look for where the shadings overlap. The overlap is the set of solutions. Graph the set of solutions to the system below.
 x2 + y2< 64               x+y ≥ −5               10 > 2x−y
• It usually helps to begin by putting the inequalities in a format that is easy to graph, like one where y is alone on one side. However, it is not always the case that having y alone on one side is the easiest way to know how to graph something. You might already know from previous math classes (if you don't, and are curious to see more, check out the lessons on conic sections) that an equation of the form x2 + y2 = r2 gives a circle of radius r that is centered at the origin. Thus, we see that the first inequality describes a circle of radius 8 (since 64=82). For the other two inequalities though, it will be useful to put them in the normal form:
 x+y ≥ −5     ⇒     y ≥ −x −5 ⎢⎢ 10 > 2x−y     ⇒     y > 2x −10
• Plot out a line or curve based on each inequality. While plotting, treat it as if it were a normal equation that you were graphing. The only thing to keep in mind is that ≤ and ≥ get solid lines, while the strict inequalities of < and > get dashed lines.
• Once every line/curve is plotted on the graph, (and solid or dashed, according to the inequality type), shade each one according to its inequality. This can be done in one of two ways. First, if it's structured to have y alone on one side (like our two lines are), you can look at the "direction" of the inequality sign. If the y is greater (y ≥ or y > ), then we shade above the line. If the y is lesser (y ≤ or y < ), then we shade below the line. Alternatively, if you're not sure of the above or the inequality is not in slope-intercept, choose a "test point" on the graph. Plug it in to the inequality. If it works, shade the side that the test point is on. If it does not satisfy the inequality (it "breaks"), shade the opposite side. This testing method works well for the circle. If we test (0, 0) in the circle's inequality, we get that 02 + 02< 64, so the test point satisfies the inequality, meaning we should shade the inside of the circle.
• Once you have shaded each of the inequalities, look for where the shadings overlap. The overlap is the set of solutions. A right triangle has a hypotenuse of length 53 meters and a perimeter of length 126 meters. What is the length of each of the triangle's legs (the non-hypotenuse sides)?
• If you have difficulty understanding the problem, begin by sketching out a picture of it. Let's call the two unknown legs a and b. We can connect the two legs to the hypotenuse through the Pythagorean Theorem: the sum of each leg squared then added together equals the hypotenuse squared.
 a2 + b2 = 532
We can also connect the length of all the sides through the perimeter. By definition, the perimeter is the sum of the lengths of all the sides, so we have
 a+b+ 53 = 126
• From here, we have a system of equalities to solve. Let's solve for b in the perimeter equation:
 a+b+ 53 = 126     ⇒     b = 73 − a
We can now plug this in to the Pythagorean Theorem equation:
 a2 + b2 = 532     ⇒     a2 + (73−a)2 = 532
• We see that we will be working with a polynomial equation, so expand, simplify, and get everything on one side:
 a2 + (73−a)2 = 532     ⇒     a2 +5329 − 146a + a2 = 2809     ⇒     2a2 −146a + 2520 = 0
Since the numbers are so large, it would be a little difficult to solve this by factoring (but not impossible), so let's use the quadratic formula:
a     =     −(−146) ± √ (−146)2 − 4(2)(2520)

2(2)
=     146 ±34

4
Thus, there are two possibilities for a:
 a = 146+34 4 =     45 ⎢⎢ a = 146−34 4 =     28
[Eeek! Shouldn't we be worried about the fact that we just got two answers for a? It is a word problem after all, and it doesn't make sense for a length to be two things simultaneously. However, don't worry. This will clear itself up shortly.]
• Let's now try using one of the possible values we have: a=45. Plugging that in, we can find b:
 b = 73 − a     ⇒     b = 73−(45)     =     28
Thus, if a=45, we have b=28. Similarly, if we try using a=28, we get
 b = 73−a     ⇒     b = 73 − (28)     =     45
So if a=28, then we have b=45. Therefore, the two sides are length 28 m and 45 m. [This clears up why we got two values for a from the quadratic formula. Because the two legs must come out to be 28 and 45. We don't know which one a represents, so it could be either. But whatever a winds up being, b must be the other value.]
28 meters and 45 meters
Two cars are driving on the highway. Car A is traveling at a constant speed of 20 m/s and the distance traveled by car A in t seconds can be modeled as
 dA = 20t.
Car B starts 100 m behind car A and at a speed of 15 m/s. Unlike car A, though, B is accelerating at 1 [(m/s)/s]. The distance traveled by car B in t seconds can be modeled as
 dB = 1 2 t2 + 15t.
How much time does it take for car B to pass car A?
• While the problem tells us how to connect the distance the car has traveled to the time elapsed, it does not directly tell us what the location of each car is at a given time. We must first set that up. At t=0, arbitrarily say that car A is at the starting location of L=0. Thus, after t seconds, car A's location will be
 LA = 20t.
For car B, we do a similar thing, but we want it to be based on the same location system that car A is. Thus, we need to know where car B is relative to car A at t=0. According to the problem, car B starts 100 m behind car A, so B must have a starting location of L=−100. Thus, after t seconds, car B's location will be
 LB = 1 2 t2 + 15 t − 100.
• At the moment when car B passes car A, they must have the same location. Thus, we want to consider when LA = LB. We can now set the right side of each equation equal:
 20t = 1 2 t2 + 15 t − 100
Now we solve for the time t.
• It's a polynomial equation, so get everything on one side:
 20t = 1 2 t2 + 15 t − 100     ⇒     0 = 1 2 t2 −5t − 100     ⇒     0 = t2 − 10t −200
• If you can't see how to factor it, just use the quadratic formula. But we might see that we can factor it as
 0 = t2 − 10t −200     ⇒     0 = (t+10)(t−20)
Thus the two possible times (from the equation) are t=−10 and t=20. However, it makes no sense to talk about negative time, since we don't know what was happening before the start of the problem. We only know what happens in positive time, so that is our answer.
20 seconds

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.

### Nonlinear Systems

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

• Intro 0:00
• Introduction 0:06
• Substitution 1:12
• Example
• Elimination 3:46
• Example
• Elimination is Less Useful for Nonlinear Systems
• Graphing 5:56
• Using a Graphing Calculator
• Number of Solutions 8:44
• Systems of Nonlinear Inequalities 10:02
• Graph Each Inequality
• Dashed and/or Solid
• Example 1 13:24
• Example 2 15:50
• Example 3 22:02
• Example 4 29:06
• Example 4, cont.

### Transcription: Nonlinear Systems

Hi--welcome back to Educator.com.0000

Today, we are going to talk about non-linear systems.0002

Previously, we have only worked with linear equations or inequalities.0005

But a system is not required to be linear; a system of equations or inequalities is just multiple relations that are true at the same time.0009

It is just different things that we know are all true at the same time; that is a system.0018

For example, we could look for the solutions to the system x = y2 and 3x + 6y = 9.0022

For it to be a solution to the system, it has to be some (x,y) pair that makes both equations true at the same time.0029

It has to satisfy each part of our system.0035

Solving the system will end up being very similar to solving a system of linear equations.0038

We will look at how we can apply the three methods of substitution, elimination, and graphing,0042

just like we talked about when we were solving systems of linear equations.0047

After that, we will also look at finding solutions to a system of non-linear inequalities.0050

It would be helpful to watch the previous two lessons, if you are just jumping to this one as the first one on these things.0054

We will be reviewing methods, but we won't be really teaching any of them in-depth.0059

So, if you really want to get the chance to learn substitution/elimination/graphing, it would be great to watch the previous ones.0062

But if you have already seen them, you are good to go.0068

All right, substitution is the most fundamental way to solve any system of equations.0070

You just put one variable in terms of the other, or the others; then you substitute it in, and you work through a solution.0074

For example, we have x = y2, 3x + 6y = 9; well, we notice that we have x here; we have x here.0080

So, we can plug in, and we will have 3 times what it was over here, y2, plus 6y, equals 9.0087

We have 3y2 + 6y = 9; it is nice not to have as many numbers.0097

We see that we can divide by the number 3: we have y2 + 2y = 3.0105

At this point, we look, and we say, "Oh, that looks just like solving a polynomial; let's do it like we are solving a polynomial."0111

So, we move everything over, so that we have a 0 on one side: we have y2 + 2y - 3 = 0.0117

We see...can we factor this? Yes, it is not too difficult for us to factor.0123

We find (y + 3)(y - 1) = 0; we check that; y times y is y2; good; -y + 3y gets us +2y; good; 3 times -1 is -3; good.0128

At this point, we can solve for what our y's are going to be.0146

We have y + 3 = 0 as one possibility; y - 1 = 0 is another possibility; we have y = -3 and y = +1.0148

Those are our two possible worlds; so, in one world (let's make it the red world), we have y = 1.0158

Now, we can solve for what our x is going to be by just plugging it in.0166

x = y2; so now, we plug it in: what is x going to be when y is 1?0171

We plug that in; x = 12, so x = 1.0176

So, in the red world, when we plug in y = 1, we get x = 1; so we have the point (1,1) as an answer to both of these equations.0181

However, we also have another world that we can check out; let's make this one the green world.0191

We have y = -3; so what happens when we plug that one in?0195

We will end up having x = (-3)2; so we have x = +9--that is the other one.0200

So, in the green world, we have x = 9; y = -3; (9,-3) is the other point that would solve this.0209

And that is how you do it by substitution; you just get one variable on its own, plug it in, swap out the other ones, and then work your way to a solution.0217

In elimination, we add a multiple of one equation to the other to eliminate variables.0225

In this case, if we have x = y2 and 3x + 6y = 9, well, we notice that we have x's here; we have x's here.0229

We can make the x's on our left be the same number as the other one, but opposite (negative).0236

So, let's multiply everything by -3; we have -3x = -3y2.0240

So now, we can bring this over; we can add it over; and we have + -3x = -3y2.0247

We can add that on either side: 3x and -3x cancel out; we have 6y = 9 - 3y2.0255

We move this over; we have 3y2 + 6y - 9 = 0.0265

This is starting to look familiar; we divide everything by 3; y2 + 2y - 3 = 0.0271

And now, we are just where we were with substitution, at this point.0278

We solve this like a polynomial to figure out what our values of y are.0281

And then, we use that to figure out what our values of x are going to be.0284

What are our possible values of y?--we figure out our possible values of x from that.0287

That is how we would use elimination.0292

Now, in general, elimination, I would say, is less useful for non-linear systems.0294

It still works, but it can be difficult to eliminate variables, because the equations aren't linear, so they don't match up as easily for cancellation.0299

In this one we have here, we have y2 over here, but y2 doesn't show up anywhere over here.0307

There is no y2 over here, so we can't try to cancel out y2.0314

We were lucky enough that we had an x in one of them and an x in the other one, so we could cancel out x terms.0318

But we can't necessarily cancel out everything, because there are various ways.0323

Since we are no longer stuck with just being limited to using linear things, we can have all sorts of weird things.0327

We could have sine of x, exponential function of t...all sorts of things for our variables that make them not really fit together.0332

So, elimination doesn't really work that well.0341

It is still useful and useable when you are in the right situation, so you can keep a lookout for it.0343

But don't rely on it as much as you do when you are working with linear systems.0348

Graphing: we can also graph each equation in the system.0353

Wherever they intersect is a solution to the system.0356

Remember: this is because a graph shows us all of the points that are true; all of the solutions to a single equation are its graph.0358

So, if we find a solution to both of our equations at the same time, that would have to be on both of the graphs at the same time.0365

So, wherever they intersect is a location that is a solution to both systems, because it is on both graphs.0371

Cool; so if we had x = y2 and 3x + 6y = 9, we could look at this and say,0381

"x = y2 ends up making the red curve; 3x + 6y = 9 makes the blue curve."0387

They intersect at those locations, and so those are our solutions; great.0394

Now, if you have a graphing calculator, you can use that to find the points of intersection for the system.0399

Remember: graphing calculators are this really great tool for being able to quickly find it.0403

If you can graph the two of them, wherever the two graphs intersect on your graphing calculator,0407

you can tell it to calculate what is the value of that intersection point, and it will just put out the numbers to get that intersection point.0411

Now, if you are going to do this, you have to first put equations into the form y = stuff involving x--0418

y = stuff involving some other variable, because that is how the graphing calculator takes things in.0427

So, you would have to get this x = y2, 3x + 6y = 9, into the forms that will be y = things.0432

So, for example, 3x + 6y = 9: we would have 6y = -3x + 9.0438

We divide everything by 6, and we would have y = -3/2x + 3.0443

And so, that is our blue curve, right there.0450

We could plug that into a graphing calculator, and that would appear.0452

x = y2 is a little bit different; we have x = y2, but we want to get y on its own.0456

To do that, we take the square root of both sides.0461

But remember: if you take the square root of both sides, you have to have a plus or minus show up.0463

We have ±x = y; but that is two equations at the same time.0469

That is positive and negative; so we have to take this, and we split it into two different things.0474

We split it into y equals the positive √x, and y equals the negative √x.0478

And so, that gives us...the positive √x is the top half of our sideways parabola, and -√x is the bottom half of our sideways parabola.0488

So, if we plugged in all three of those into our graphing calculator, we could then use the intersection ability to figure out where they are going to be.0498

If we just solved for y = +√x and put in just the top half, we would end up getting only one of the answers, and miss the other one.0504

So, it is important, when you are working through with a graphing calculator,0511

to really pay attention to how you are getting this into a form that you can plug into your graphing calculator.0513

Is this really the same as the equation I started with?0518

OK, the number of solutions isn't going to be as fixed as it was when we were dealing with linear systems.0522

When we worked with linear systems, there were only three possibilities for the number of solutions.0529

There was going to be one solution, no solutions whatsoever, or infinitely many solutions (when we just ended up having the same line on top of itself).0534

But with a non-linear system, all guesses are futile; there can be any number of solutions at all.0541

The only way to figure out how many solutions there are is by solving the system or by looking at a really good graph of it.0546

For example, with this one on the left, we end up seeing that it has three solutions, because it intersects here, here, and here.0551

And this one just has a crazy, huge number of solutions, because we have the first intersections.0559

But then here, we have one here and here and here, and then it just starts to pack in and pack in and pack in0564

as we get closer, because that red graph is going up and down really, really quickly.0569

So, you end up seeing lots of solutions in some cases.0573

You won't end up having to work with any in there--any like this; it would probably be a little too difficult at this point.0576

But just understand that the number of solutions that you are going to get out of a non-linear system isn't any fixed value.0581

It is not like linear systems, where you can rely on knowing that it is going to just be one.0588

There is no known number that it is going to be, and the only way to work it out is by working it out.0591

Systems of non-linear inequalities: when we are working with non-linear inequalities, it is basically the same as when we were working with linear inequalities.0597

The first step is to graph each of the inequalities.0605

Graph it; and the way you graph it is as if it were an equation.0608

Oops, there was a mistake in the graph here; we will fix it in just a second.0612

So, you graph them as if they were equations with lines.0616

However, you don't necessarily just use straight lines all the time.0619

If it is dashed...you use dashed when it is a strict inequality--strictly less than or strictly greater than.0621

Notice: in this case, we have that y is strictly greater than 2x2 - 5.0629

So, this red one is the graph of 2x2 - 5; it needs to be dashed, because it is a strictly greater than.0633

Let's go through and dash that, really quickly; that is how it should look--it should be dashed.0641

OK, a dashed line is for the greater than, because it is saying, "If you are actually on the line-- if the point is on the line--it is not a solution."0656

And then, after that, you shade it appropriately--you use test points to help you figure it out.0665

So, for this one, let's use (0,0), since neither of the lines falls straight on (0,0); it makes a great test point.0669

If we plug that in to y > 2x2 - 5, we have 0 (for y) > 2(0)2 - 5.0676

0 is, indeed, greater than -5, so that checks out.0686

We know that the side that we are going to be shading in is the side facing this purple dot for our red equation.0690

So, we shade in this stuff here; OK.0701

Now, the blue curve is less than or equal to 1/5x2 + 2; that is our blue curve, right here.0707

Let's use that same test point: we plug in (0,0); let's check what happens with that.0715

Plug in 0 for our y; 0 ≤ 1/5(0)2 + 2; and indeed, 0 is less than or equal to 2.0721

So, that checks out; that tells us that we are going to have the blue side shade towards our purple test point.0730

We shade towards our purple test point, so we are shading everything underneath and including that blue curve.0737

So, everything underneath this blue curve is included in this inequality.0749

And everything above the red parabola is included in this one.0757

The part where they overlap is the space between the two parabolas.0762

So, we can color that out; now it is getting a little confusing to see things, but see, we color that out with the purple;0768

and we can see that this is the space that satisfies our system of inequalities,0774

because if you are inside of this space, you end up being true for both of the inequalities at the same time.0782

And that is how we figure it out; we shade it, and we will be able to figure it out by shading--0790

each one of them individually, and then where all of the shadings agree--0793

where all of the shadings overlap--that is our set of solutions; that is the set of points that satisfies our system of inequalities.0796

All right, we are ready for some examples.0803

The first example: xy = 2; we want to get something where we can plug it into the other one.0805

Well, we see y = -1 + x, so let's take this; we will swap out y for -1 + x.0811

We plug that in over here; we have x times the -1 + x for y; -1 + x = 2.0823

Multiply our x over; we have -x + x2 = 2; this looks like a polynomial, so let's solve it like a polynomial.0833

x2 - x...subtract the 2 over...we have x2 - x - 2 = 0.0842

At this point, we factor; x looks like it is going to have minus 2, and x + 1.0848

Check it really quickly in our head: x times x is x2--great; x + 1...so 1x - 2x gives us -x; -2 times 1 is -2; great--that checks out.0856

So, at this point, we can solve for it: x - 2 = 0, or x + 1 = 0.0865

Those are the two possible worlds: we have x = 2 and x = -1; great, those are our two possibilities.0870

I will arbitrarily choose two different colors for them; let's make the green world be when x = 2;0878

we can plug it in over here; x = 2...actually, we can plug it into either one.0884

It looks to me like it is probably a little easier to plug it into this one.0889

But we could plug it into either of the equations, if we wanted.0893

We have y = -1 +...1x is 2, so y = -1 + 2; that gets us +1.0895

Our first point that we figured out is (2,1)--our first answer.0904

Then, we will arbitrarily choose another color; in the purple world, we are going to have x equal to -1.0912

When x = -1, we plug that one in; so we have y = -1 plus the x value that we are plugging in, -1.0918

So, y = -1 + -1; that gets us -2, so that gives us the point...x value of -1, y-value of -2; and that is our two solutions.0928

Our purple solution and our green solution are all of the solutions to this system.0940

All right, the next example: Find the solutions to this system.0945

In this case, we see that y is already over here, just by itself; so it looks like an easy candidate for substitution.0948

Let's plug x2 + 2 in for y over here.0955

We plug that in; we have x2 + 2, since that was what y used to be; that equals...0958

oops, squared: we have to have everything continue to be the same...x - 1.0965

x2 + 2, squared, equals x - 1; at this point, that might raise our suspicions a little bit.0970

But let's keep working it out and see what happens.0977

So, that gets x4 + 4x2 + 4 = x - 1.0980

This might start to raise our suspicions about what we are looking at.0989

Is it possible for this equation to ever be true?0993

Is there some x-value that would make the left-hand side the same thing as the right-hand side here?0996

Well, let's keep working it out and see if we can get something that will make it obvious what we are looking at.1002

x4 + 4x2 + 5 = x; OK, if we look at this, we might realize that we could try to solve it from this point;1006

but we aren't certain that there are solutions: it said "If possible."1018

We want to be just a little bit suspicious, because it can be a real pain to try to solve something for a long time,1023

if it turns out that it is impossible to solve; so you want to be able to figure out if this is possible to solve,1028

before you get too deep into the process of trying to solve it.1032

So, x4 + 4x2 + 5...well, what does that look like--what would we end up seeing there?1035

Well, that is going to be a really, really fast-growing graph that starts at some height of 5,1041

and then shoots up really quickly: x4 + 4x2...it never becomes negative.1048

That is what the left-hand side is equal to.1052

But the right-hand side, x--what would that end up being?1054

That is going to be here; and if we graphed just x, that would go like this.1058

Now, we are appealing to a graph to understand this, but we see that the left-hand side1063

is going to always be putting out much larger numbers, no matter what x we put in,1067

than the right-hand side is ever going to be able to put out.1070

We have x4 + 4x2 + 5; that is going to make really big numbers, always positive, really quickly.1073

Now, x can end up getting large positive numbers, but it has to put in a very large x to do that.1078

And if we put in a very large x on the right side, the left side will be enormous.1083

So, we see that these two sides can never match up; so our suspicion is that there are actually no solutions here.1087

We could try to move that x over and have it equal 0.1094

But remember: some parabolas/some...in this case, it is not a parabola, because it is a fourth-degree...1096

but some polynomials don't have solutions; they never touch the x-axis,1102

if we are searching for when it is equal to 0; we are searching for roots.1107

So, we end up being able to figure out that this won't work.1110

But we want something that really makes it more obvious than just having to turn this into an equation and see this.1114

It just seems a little bit uncertain; so the best way for this is actually going to be to graph it.1120

If we graph it, we will see that this very clearly can never work out.1125

We can graph both of our original equations, x2 + 2 = y and y2 = x - 1.1130

We will make a tick-mark length of 1, 3, 4...go up to 4 on each...1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4.1138

Great; so let's first graph the easy one, x2 + 2 = y.1152

That one is pretty easy for us to graph; we will graph this one in blue.1157

x2 + 2 = y; well, we start at a height of 2; we plug in x = 0, and we get a height of 2.1162

Plug in x = 1; now we are at a height of 3; with -1, the same thing; at 2, we will be way out at a height of 6.1170

So, we see that we are going to curve out very quickly; we are going to shoot out like this.1177

That is what the curve ends up being; don't get that part confused--the graph is not actually connecting to that circled part.1182

The blue graph goes to x2 + 2 = y; what about y2 = x - 1?1189

Now, we are used to solving things in terms of y = stuff; but that is actually not going to be the easiest way to do this,1194

because then you have to take square root, and you have a positive and a negative side, because it is plus or minus square root.1202

What we can do is y2 + 1 (we add 1 to both sides) = x.1207

And so, we can solve this from y's point of view, as being the input, and x being the output.1212

For example, if y is 0, what does x end up being?1216

If y is 0, then x ends up being 1; so at y = 0, a height of 0 on the horizontal axis, x will end up being positive 1.1220

0 squared, plus one, equals positive 1.1230

At a height of 1, when we plug in y = 1, x will end up being 12 + 1, or 2.1234

At a height of 2, when y is at the height of 2, we plug that in; we have y2 + 1, so 22 + 1; 4 + 1;1242

5 is going to be our x-value, somewhere out here.1252

The same thing happens if we plug in a negative height: -1 will end up getting us an x-value of 2.1255

-2 will end up giving us an x-value of +5, as well...1260

I'm sorry: did I say -2 for -1? A height of -1 will give us an x-value of +2, just in case I said the wrong thing back there.1264

And then, we curve this out like this, because it is going to be a parabola, as well, because it is of that degree.1271

Curve that just a little bit better, so we can see it more accurately.1279

Curve that like this; it goes out like this.1284

So notice: the red one is going to keep going out to the right; the blue one is going to keep going up.1290

They are never going to end up touching each other.1295

This cup goes like this; this cup goes like this; they go out like that.1297

They are never going to touch each other; they are never going to intersect.1301

There is no way for these things to ever connect to each other.1304

They can't ever connect to each other, because we see that when graphing them, they fail to ever touch.1308

With that in mind, we see that there are no solutions to this system.1313

All right, next: Graph the solutions to the system of inequalities: y < 3cos(x); y ≥ x2; and x < 1.1321

Now, we haven't explicitly said that we are going to be using trigonometric things.1330

But we are basically at that point, where we are going to assume that you have gone through the trigonometry lessons.1334

So, you are probably used to it; if you are not used to it, just trust that I am giving you an accurate depiction of how 3cos(x) works.1339

y < 3cos(x); the first thing we do, let's set up a nice, large graph, because we are trying to graph the solutions to the system of inequalities.1345

Since we are working with cosine, we know that we are going to want it at least out to 2π on either side.1355

So, π is 3.14; 2π is 6.28, approximately; we want to go out to probably at least 7 marks horizontally in either direction.1360

A tick mark will be a length of 1; so 1, 2, 3, 4, 5, 6, 7...I actually drew a little bit more than was necessary;1371

1, 2, 3, 4, 5, 6, 7; up 1, 2, 3, 4, 5, 1, 2, 3, 4, 5; OK.1382

Let's graph each one of these: first, we will graph y < 3cos(x) in green.1400

Now, notice: it is less than, so it is going to be dashed.1406

Let's get some points, so that we can draw in this line properly.1408

If we plug in x = 0, remember: we are in radians; we are not using degrees here; otherwise our x-axis would have to be huge.1412

So, with radians, if we plug in 0 (x is 0), then we are going to have a cosine of 0 put out 1;1419

so we will have 3 times 1, so we will be at a height of 3 when we are at a horizontal location of 0.1425

Halfway, at π/2, which is a little bit over 1 and 1/2 (1.5 and a little bit), we will be at 0; cos(π/2) is 0; 3 times 0 is 0.1431

The same thing if we go over to the negative π/2, around halfway between 1 and 2.1445

Then, at π, we are going to end up having -3, because cos(π) is -1, so 3cos(π) will be -3.1452

So, 3.14 is a little bit past the 3 marker over here.1463

And then, the same thing happens over here at -π; so -3...a little bit past the -3 marker...1470

We can curve out what cosine looks like, and what we knew before, in this portion right here.1478

All right, OK, we can do the same thing with continuing this graph out.1493

We know that at 2π, 1, 2, 3, 4, 5, 6...around 6.28 we will be back up to a height of 3.1498

We know that, halfway between the two, at around 4.6 or 4.7 or so, we will be at 3π/2; 1, 2, 3, 4...1509

And a little bit over halfway, we will be back at a height of 0; the same thing going the other way: 1, 2, 3, 4...1519

a little bit over -4 1/2...and then 5, 6...a little bit over 6; and there we go...a little bit over -6.1526

We can curve in a little bit more of this, like that.1536

Now, notice: at this point, I technically made a mistake, because was it a strict inequality?1545

Yes, it was a strict inequality; it was strictly less than.1553

So, if that is the case, we can't be using a solid line; we have to be using a dashed line.1556

It is a little bit easier for me to draw it; I am just going to come in with my eraser, and I am going to erase this into being dashed,1561

which I am sure we have all done at some point--where we accidentally draw something as solid,1566

and realize, "Oh, I have to make this dashed now."1571

We came through with an eraser and just erase it into a dashed form.1572

At this point, we have y < 3cos(x); at least, the line, the curve generated by it, graphed in.1581

We will shade it in, in a little bit.1587

Next, we will do y ≥ x2 in blue.1589

This one is much easier--we know it: x is 0; we are at a height of 0; at 1, 1; at 2, +4;1593

the same thing on the other side: -2, +4; and we curve out, just in a nice, handy parabola--much faster.1600

And since it is greater than or equal to, it actually makes a solid line, because it is not a strict inequality; it is not strict.1611

And then finally, x < 1 we will do in red.1619

That means that x has to be something less than 1; so that means we have fixed x at 1 for drawing the actual graph, for drawing the curve.1622

We are going to fix x at 1, and then we will see that y is allowed to go to anything it wants,1630

because for x < 1, y can be anything it wants; x < 1 doesn't care what y is.1636

So, we fix x at 1, and we draw a dashed line, because it is a strict inequality.1641

It says that x has to be less than 1--it is not allowed to actually be equal to 1; we have a dashed line for that.1647

So now, we do some shading and figure out what is allowed for each one of these.1653

y < 3cos(x): we could do a test point at (0,0); 0 < 3cos(0), so 0 < 3.1657

That is perfectly true, which makes sense, because y <...also means that we are going to be looking at the part that would be below the curve.1667

So, what is below the curve? Stuff like this.1674

I am not doing a very extreme job of shading, just because we want to have some idea of where we are looking.1681

So, we don't have to shade too much right now, until we figure out where they all agree.1685

y ≥ x2...we can't use the test point (0,0) because it is actually on our line; so we have to choose a new one.1689

Let's try (0,1): 1 is greater than or equal to 02...indeed, that is true.1696

Also, since it is y ≥, we know that it has to be above the curve.1701

So, what is above the curve is this stuff here; great.1705

And then finally, if x < 1, we have to be to the left side of it, because our x-value has to be below it.1710

We could also use a test point, like (0,0); we don't care about the y-value, but 0 is less than 1, so we shade towards that test point of (0,0).1717

So, we would go in to the left; great.1724

At this point, we have seen that the only thing that they can agree on is this little part right in the middle that we are now shading with green.1728

And there we go; and that is how we figure out where these things go; cool.1741

All right, Example 4: A rectangular box has the following properties.1747

The sum of its edges is 24 feet; adding together the area of each of its faces gives a total of 22 square feet;1750

its height is twice its width; and then we are asked to find out what its volume is.1756

The first thing to do is: we want to get a sense of what we are looking at, so let's draw a quick picture.1760

If we have a box, some box, it has three things to it: length, width, and height.1764

We can see that; we have...what is its length? What is its width? And what is its height?1779

Great; with that in mind, let's start trying to figure out how these properties turn into math.1791

The sum of its edges is 24 feet; now technically, we don't really know: are they saying just one of its edges each time?1797

Or are they saying all of its edges?1805

So sometimes, you end up seeing things that are a little bit confusing in math.1807

And if you saw this on a test, it would probably be a good idea to ask your teacher, because you are not sure.1810

Does that mean h + w + l, or does that mean each edge of the box, all added together?1814

Let's go with the sum of every edge; let's say that is what it means.1820

But notice how each of its edges...the sum of its edges...well, that could be considered to just be the three edges,1826

the fundamental edges (height, width, and length); but it could also be all of the times that they show up on the box.1831

If you have a rectangular object, it shows up here and here and here.1837

Height actually shows up four times, because we have each of the columns that make up our box.1840

We have a height here, a height here, a height here, and a height here.1847

So, we can think of it, if we are looking at every edge, as 4(height) will be part of what is going in that.1852

So, the sum of not just its edges, but every edge, is how we will do this problem.1858

All right, so if that is the case, this first thing is going to end up coming out to be...1863

The first idea will come out to be 4h + 4w + 4l = 24 feet.1869

So, height, width, and length, all combined together, comes out to a total of 24 feet.1881

because it is the sum of every edge, every one of the edges, and each edge...1886

height will show up 4 times; width will show up 4 times on the box; length will show up 4 times on the box.1890

If 4you find this confusing, try just finding some rectangular object that you can look at;1896

pick up an actual box and count the edges--count how many times its height shows up.1899

Any rectangular box will be able to show you this idea, if it is a little confusing.1903

Physical things are a great way to explore things in math.1906

Next is adding together the area of each of its faces.1910

This one is a little bit tougher: how many times does, let's say, this face right here--the very front face--show up?1913

Well, we see that height times width would be the area of that face.1920

So, height times width is going to get multiplied together.1924

But it doesn't show up just on the front; it also shows up on the back side.1929

It is the front side, but also the back side--both sides.1934

So, it is not going to be just h times w, but 2 times h times w.1936

By that same logic, each of the side faces...we are going to have l times h, because it is h over here...1942

so the side faces will show up twice, as well; so we have 2lh.1950

And then finally, the top face is going to be the length times the width, so 2 length times width.1956

And we were told that that came out to be 22 square feet total.1970

So, we can find the area of each one of the faces; hw will be one of the faces, and then it doubles up each time.1974

lh will be the area of one face; it doubles up, and so on, and so forth.1979

So, we have 2hw + 2lh + 2lw = 22; and then finally, we were told that the height is twice its width.1983

That is probably the easiest one of all: if the height is equal to twice the width, it is 2 times the width; great.1990

At this point, how do we find volume--what is volume based on?1997

Well, if it is a nice rectangular box, volume is just equal to all three of these variables, multiplied together: h times l times w; great.2000

That is all of the steps that we need together to be able to figure out what this is going to be--2009

to be able to get this in a position where we can solve it.2013

So now, let's start working it out.2015

We have 4l + 4w + 4h = 24, 2lw + 2wh + 2lh = 22, and h = 2w.2017

And we are looking for volume, which is going to be l times w times h.2024

Great; so I would say that the very first thing to do...let's take 4l + 4w + 4h, and let's make it a little bit easier.2028

Let's divide everything by 4; we have l + w + h = 24/4, which gets us 6.2033

The same thing over here: let's divide everything by 2, so that gets us lw + wh + lh = 11; great.2040

So, at this point, we can actually start figuring things out.2051

Let's try to solve in terms of w; we have w over here; h is already ready to be substituted in somewhere.2053

So, since it is connected to w, we can probably figure out w easiest from what we have set up here.2061

We can plug that in over here: if h = 2w, then we have l + w +...what was h equal to? h was equal to 2w, so + 2w = 6.2066

l + w + 2w...3w = 6, so l = 6 - 3w.2080

Now, at this point, we are ready to substitute l in, as well.2087

We have h ready to substitute and l ready to substitute; so we can now go into our big equation, lw + wh + lh = 11.2090

So, we plug in here: l is 6 - 3w, so (6 - 3w) times w, plus w times...h is 2w...plus l...l is (6 - 3w), times h...is 2w; equals 11.2097

6 - 3w times w...w distributes, so we have 6w - 3w2, plus...w distributes onto 2w...2118

well, not "distributes," but 2w2 + (6 - 3w)2w...6 times 2w becomes 12w,2126

minus 3w times 2w, becomes -6w2; equals 11.2134

Great; let's simplify things a bit; we have -3w here; plus 2w2 here; and -6w2 here.2139

So, -3w2 + 2w2 gets us -1w2; - 6w2 brings us to a total of -7w2.2146

Our 6w and 12w combine to +18w, equals 11.2154

We have squared; we have a single degree of 1; and we have a constant; this looks like a polynomial.2160

Let's get it into an easy-to-solve polynomial format.2166

At this point, we could toss this into the quadratic formula and solve out the answers.2173

But we might be able to get lucky; and even though it looks a little complex, we might realize that we can factor this.2178

It is not too difficult to factor.2183

We get lucky; we notice that it turns out pretty easy to factor: 7w and w here...2184

We need to have minus on both of them, because it comes out to be positive 11.2194

Minus 18w...we have a 7w here, so this will be -1, and this will be -11.2198

7w times w is 7w2; 7w - 1 - 7w...minus 11 times w...minus 11w; so -7w - 11w is 18w; it checks out; -11 times -1 checks out as a positive number.2203

Great; it is always a good idea to check when you are factoring.2216

So, we can now solve each one of these: 7w - 11 = 0, or w - 1 = 0.2219

We actually have two different possible worlds.2226

It didn't say that in the problem, but there are two different possible worlds for what the width of the box can be.2228

It can be 11/7 or 1; so 11/7 and 1 are our two possible things.2235

So, let's call these, arbitrarily...we will make colors for these.2241

w = 1 looks easiest to solve and deal with first, so we will make that the purple world.2246

w = 1--if that is the case, we can figure out that h = 2w; we plug that in; h = 2(1), so we have that h is 2.2250

And then, we also have, if it is w = 1...we plug that into l = 6 - 3w; so l = 6 - 3(1); so 6 - 3 = 3.2261

We have w = 1, h = 2, l = 3 in our first world, in this purple world,2276

because remember: there were two possibilities for what our width could be.2284

But if this is the case, then our volume is going to be the three of these multiplied together: 1 times 2 times 3, which equals 6.2287

So, one possible value for our volume is going to be 6 cubic feet--that is one possible answer.2294

It turns out that there are two different worlds here, so we want to check out both of them.2305

The other one: we will make this the green world, where the width is equal to 11/7...2308

Well, if width equals 11/7, then we can plug that into h = 2w, so h = 2(11/7), which equals 22/7.2312

So, if our width is 11/7, then our height is 22/7.2323

And then, we can also figure out what our length is going to be.2331

Length equals 6 - 3w; w, in this case, is 11/7; so we have 6 - 33/7, which ends up simplifying out to 9/7; great.2335

At this point, we have width = 11/7; height = 22/7; and length = 9/7, all of these in feet as the units.2350

So, at this point, we know that the volume is equal to each one of these, multiplied together:2363

so 11/7 times 22/7 times 9/7; we multiply these all out together, and it becomes 2178/343,2366

which is really not that easy to see what that means.2380

So, let's approximate that using a calculator; and that comes out to be 6.35.2383

So, our other possibility is that the volume comes out to be 6.35 cubic feet.2389

So, it turns out that there is actually a larger possible box if we are not going with these nice, friendly integer things.2396

But we can still follow the three requirements; there are three conditions that were given to us.2402

It turns out that there are two possible boxes that actually fit those conditions; and those are the volumes.2407

In our purple world, where our width was 1, we got 6 cubic feet.2412

And in our green world, where our width was 11/7, we got 6.35 cubic feet.2415

And if you wanted to check this--if you wanted to make sure that everything was great--2420

a good thing to do would be to see that you have width = 1, height = 2, length = 3,2423

and then just try plugging that into each of these three equations that we started with,2429

and making sure..."Yes, that checks out; yes, that checks out; yes, that checks out."2433

The same thing over here for the width = 11/7, height = 22/7, length = 9/7:2437

you can just plug that into each of these three equations, and make sure that it checks out in each one,2447

because if it checks out in each one, you know that that is a workable answer.2452

All right, that finishes our work with systems of equations of all types.2455

And we will see you at Educator.com later--goodbye!2459