Evaluating Expressions with Substitution

Evaluating Expressions with Substitution

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Sports

• We substitute player for player in sports to give breaks. In order to substitute with the best outcome, you want to make sure they play the same position.

• It is the same thing with expressions. When we substitute, we will put in a number for the letter that it is equal to. The number and the letter are playing the same position.

• Example: If x=4, we can plug 4 in anywhere we see an x.

Multiple Choice

In sports, you substitute players into different positions then they usually play.

• True

• False

Substituting and Evaluating

When you are given a number to plug in a variable's place, you are able to evaluate an expression.

Example 1: 3x; x=4; would give you 3(4), which equals 12.

Example 2: 3x+2y; x=5, y=4; so 3(5)+2(4)= 15+8=23

Multiple Select

Select all of the options that are examples of substitution.

• 3x, x=4, so 3(4)

• 3y, x=2, so 3(2)

• 2+x, x=2, so 2+2

• 2+y, x=4, so 2+4

Evaluating an Expression

Sometimes you are told what number each variable equals and you must plug in the right numbers to find the answer. This is called evaluating an expression

Example: Solve each expression if a=3 and b=4

• 2+a (plug in 3 for a) so 2+3 =5

• b-2 (plug in 4 for b) so 4-2=2

Multiple Choice

x+2y; x=3, y=7

when you substitute and evaluate this problem, your answer is 17.

• True

• False

Order of Operations Review

You MUST use the order of operations to evaluate correctly.

Please Excuse My Dear Aunt Sally (PEMDAS)

Parenthesis, Exponents, Multiply/Divide, Add/Subtract

*Be sure to write this at the top of every problem and check off each step as you go.

*Remember Multiply/Divide are whichever you see first left to right. This is the same for add/subtract.

Order of Operations Example (PEMDAS)

Multiple Choice

Review Check: Evaluate the following when x=2 and y=3 $$x^3+2y-3$$  

• 11

• 9

• 28

Multiple Choice

Evaluate if c=2

4+c

• 4

• 5

• 6

• 7

Multiple Choice

Evaluate if c=6

c-3

• 1

• 2

• 3

• 4

Multiple Choice

Evaluate if b=2

4b-1

• 6

• 7

• 8

• 9

Multiple Choice

Evaluate if a=3

2a

• 5

• 6

• 10

• 12