WEBVTT mathematics/basic-math/pyo
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Hi, welcome to Educator.com.
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This lesson is on expressions and variables; let's begin.
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First thing we have to go over--variable; variable.
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A variable is a letter or symbol that can stand for or represent one or more numbers.
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In place of numbers, I have usually letters.
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If I use A or B... I can use X, Y... those are all considered variables.
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I can also use symbols.
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Sometimes in math, we use Greek symbols; or I can use star as a symbol.
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Anything that represents numbers would be considered a variable.
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Expressions; expressions are numbers or mathematical phrases that includes numbers and variables.
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Keep in mind that expressions do not have equal signs.
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If it does have an equal sign, then it would be called something else.
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It would be called an equation.
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We have different types of expressions.
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The first type is a numerical expression; numerical means numbers.
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If we have a numerical expression, it would be an expression, mathematical phrase, that has only numbers.
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Here is an example, 30 plus 5; this is considered a numerical expression.
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There is no variables; we only have numbers.
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The next one--algebraic expression--is the most common type of expression.
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That is when you have both numbers and variables.
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6 plus A is an example of an algebraic expression.
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2X minus 10 is also another example.
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We have A; that is a variable; X is a variable here too.
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2X minus 10 is an algebraic expression.
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The other type is a word expression.
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Word expression is when you use words to express your expression.
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Or you write out your expression using words.
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P divided by 9 would be considered a word expression
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because instead of writing the symbol out, you would write just--divided by--the words.
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Let's do a few examples of evaluating expressions.
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Evaluating just means to solve or simplify the expression.
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If I have a numerical expression, 12 times 20, this is a numerical expression.
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I can actually simplify this out; I can multiply 12 and 20 together.
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12 times 20; 2 times 0 is 0.
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Because it is 0, I can just move on.
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2 times 2 is 4; 2 times 1 is 2.
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When I evaluate this expression, I get 240.
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This next one, M minus 8, that is my expression.
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They want me to evaluate this expression when they tell me that M is equal to 8.
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Here is the expression; let me use black.
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M minus 8 is my expression; they told me that m is 8.
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Remember variables; this is a variable that represents a number.
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The number that it represents is 8.
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This is the same thing as 8 minus 8; my answer is 0.
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When I evaluate the expression M minus 8 when M is equal to 8, then my answer would be 0.
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The next example, I am evaluating the expression, S divided by T.
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S divided by T can also be written like this, as a fraction, S divided by T.
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They are telling me that S is 28 and T is 4; S is 28.
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Instead of writing S, I am going to write out 28
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because S is a variable that represents the number 28 and T represents the number 4.
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I can write it like this; or I can write it just 28 divided by 4.
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It is the same thing; 28 divided by 4 is 7.
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When I evaluate the expression, I get 7 as my answer.
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The final example, example four, evaluate the expression CD.
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When I have two variables next to each other like that, CD, this means C times D; C times D.
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C represents the number 3; it is 3; D represents the number 200.
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If CD means C times D, then it means 3 times 200.
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When I multiply 3 times 200, I get 600.
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When you evaluate the expression CD, when you are given the numbers that they represent, then the answer will be 600.
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That is it for this lesson on Educator.com.
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We will see you next time; thank you.