Evaluating Function Notation (ALG I)

How should you read/say "f(x)" ?

• "f x"

• "f of x"

• "f times x"

TRUE or FALSE?

The letter f in "f(x)" is another variable in the equation.

• True, it means "f times x"

• False, it stands for the word "function" as in "function of x"

Given f(x) = 8x - 12, find f(-3).

• f(-3) = -36

• f(-3) = 12

• f(-3) = -12

Given f(x) = 13 - 7x, find f(-3).

• f(-3) = 62

• f(-3) = -8

• f(-3) = 34

Given f(x) = x² - 5, find f(-3).

• f(-3) = -14

• f(-3) = 4

• f(-3) = -8

Answer explanation

Be careful on the calculator!

If you type -3² - 5, you will get the answer wrong!

Not putting a negative base inside of ( ) before plugging in the exponent means that the exponent will only apply to the number and not the negative sign.

It SHOULD be (-3)² - 5, or use "y=" and type in x² - 5 and go to the TABLE.

Given f(x) = x² - 10x + 21, find f(-3).

• f(-3) = 60

• f(-3) = 20

• f(-3) = -8

Answer explanation

Be careful on the calculator!

Not putting a negative base inside of ( ) before plugging in the exponent means that the exponent will only apply to the number and not the negative sign.

I highly recommend that you use "y=" and type in the given equation, and then go to the TABLE.

Given f(x) = x² - 10x + 21, find f(-3).

• f(-3) = 60

• f(-3) = 20

• f(-3) = -8

Answer explanation

Be careful on the calculator!

I highly recommend you use "y=" and type in the equation into the calculator, then go to the TABLE.

Given f(x) = 4x² + 14, find f(-3).

• f(-3) = -22

• f(-3) = 2

• f(-3) = 50

Answer explanation

Be careful on the calculator!

If you type 4 * -3² + 14, you will get the answer wrong!

Not putting a negative base inside of ( ) before plugging in the exponent means that the exponent will only apply to the number and not the negative sign.

It SHOULD be 4(-3)² + 14, or use "y=" and type in 4x² + 14 and go to the TABLE.

Match each FUNCTION with a CORRECT SOLUTION.

Notice: The input values are NOT all the same.

Calculator recommended, but not necessary.

• f(4) = 12

• f(x) = 11 - x

• f(-1) = 12

• f(-1) = 16

• f(x) = 0.75x + 9

• f(5) = -6

• f(x) = 5x + 21

• f(-5) = 11

• f(x) = -4x - 9