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### Solving by Substitution

To find exact solutions, use algebraic methods like the

*substitution method*.Use substitution when at least one of the coefficients in the system is 1 or –1. Solve for this variable in terms of the other one. Then substitute that expression into the other equation.

If you eventually get an equation that is always true, then the system has an infinite number of solutions.

If you eventually get an equation that is never true, then the system has no solution.

### Solving by Substitution

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
- Substitution 0:17
- Example
- Number of Solutions 1:43
- Infinite Solutions
- No Solutions
- Lecture Example 1 3:40
- Lecture Example 2 6:56
- Additional Example 3
- Additional Example 4

0 answers

Post by Reuven Farchi on December 12, 2012

Love your teaching professor, itÂ´s to the point and without talking down to you. Can you please tell me where can I find extra excercises to do in each chapter. Practice makes perfect and more so in math.

1 answer

Last reply by: jeffrey breci

Fri Jan 13, 2012 1:18 AM

Post by jeffrey breci on January 13, 2012

On example 2, I got the solution X=2, y=-1. Some how you got, x=12/7. How does -14x=-24 equal 12/7? I'm sure I won't get an answer, like everyone else on here. Collect that money people!

1 answer

Last reply by: Patryk Hebel

Sun Dec 5, 2010 8:51 AM

Post by John Barbour on November 11, 2010

The first example: 2(3y-)-6y=8 gives an answer of -2=8 Or did I do something wrong? Where are the professors? Mark asked a question on 12-11-09 and Sashka on 1-4-10 adn I still don't see an answer.

0 answers

Post by SASHKA YAKIMOVA on January 4, 2010

In Example 3, is there a reason why the second equation was picked over the first? How to determine which one to pick during an exam? Confusing...

0 answers

Post by Mark Mccraney on December 11, 2009

2:50 mark -- says the answer is nine halves, but is written correctly as 4/9