Evaluating Functions

Evaluating Functions

By Ms. Riley; credit to Gina Wilson (All Things Algebra) ---> her worksheet I made digital.

​When evaluating a function

• use the Desmos scientific calculator on your iPad.​

• make sure to put (parentheses) around the number you are substituting in for "x"​

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#1) If $f\left(x\right)=-3x-2$  , what is the value when $f\left(3\right)$  ?

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#2) If $f\left(x\right)=-3x-2$  , what is the value when $f\left(-7\right)$  ?

​Evaluating Functions

(That look hard or different)​

​First: substitute 4 in for x using ( )

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Second: add 9 to the answer

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36 is your final answer!!!​

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​USE YOUR CALCULATOR

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#3) If $f\left(x\right)=-3x-2$  , what is the value when $f\left(-2\right)+9$  ?

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#4) If $h\left(x\right)=x^2-5x+7$  , what is the value when $h\left(2\right)$  ?

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#5) If $h\left(x\right)=x^2-5x+7$  , what is the value when $h\left(-5\right)$  ?

​Evaluating Functions

(That look hard or different)​

​First: substitute 2 in for x using ( )

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Second: multiply 3 to the answer

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-18 is your final answer!!!​

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​USE YOUR CALCULATOR

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#6) If $h\left(x\right)=x^2-5x+7$  , what is the value when $\frac{1}{3}\cdot h\left(-8\right)$  ?

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#7) If $g\left(x\right)=1-\frac{3}{4}x$  , what is the value when $g\left(-12\right)$  ?

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#8) If $g\left(x\right)=1-\frac{3}{4}x$  , what is the value when $g\left(0\right)$  ?

​Evaluating Functions

(That look hard or different)​

​First: substitute 5 in for x using ( )

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Second: take (-7) and multiply it

by -2 and add 6

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20 is your final answer!!!​

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​USE YOUR CALCULATOR

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#9) If $g\left(x\right)=1-\frac{3}{4}x$  , what is the value when $-5\cdot g\left(4\right)-1$  ?

Hit the back button to see my previous example for help.

​How to use Absolute Value Sign

on the Desmos Calculator

​Absolute Value

button​

​Substitute -7 in for x using ( )

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56 is your final answer!!!​

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#10) If $h\left(x\right)=\left|1-7x\right|$  , what is the value when $h\left(1\right)$  ?

Hit the back button to see my previous example for help.

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#11) If $h\left(x\right)=\left|1-7x\right|$  , what is the value when $h\left(-7\right)$  ?

​Evaluating Functions

(That look hard or different)​

​First: substitute 8 in for x using ( )

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Second: subtract 39 from 15

(order matters)​

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-24 is your final answer!!!​

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​USE YOUR CALCULATOR

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#12) If $h\left(x\right)=\left|1-7x\right|$  , what is the value when $23-h\left(9\right)$  ?

Hit the back button to see my previous example for help.

​Evaluating Functions

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​Step 1: Substitute (3-c) in for "x"

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​USE YOUR CALCULATOR

​Using the Distributive Property

(multiplying into the parentheses)​

​Step 2: Distribute (multiply) the negative 7 into the parentheses. *Two negatives make a positive*

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​Step 3: Combine like terms

2-21=-19​

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​<--- Final Answer (simplified)​

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Multiple Choice

#13) If $$f\left(x\right)=8-5x$$  , what is the value when $$f\left(4c\right)$$  

• $$12c$$  

• $$-12c$$  

• $$8-20c$$  

• $$8+20c$$  

Multiple Choice

#13) If $$f\left(x\right)=8-5x$$  , what is the value when $$f\left(2-k\right)$$  

Don't forget to combine like terms

Two negatives (multiplied) make a positive

• $$18-5k$$  

• $$-2+5k$$   

• $$-2-5k$$   

• $$18+5k$$  

Multiple Choice

#13) If $$f\left(x\right)=8-5x$$  , what is the value when $$f\left(4p+3\right)$$  

Don't forget to combine like terms

Two negatives (multiplied) make a positive

•   $$20p+23$$  

•    $$20p-7$$  

•    $$-20p+23$$  

• $$-20p-7$$