ACT Math Practice Question: Functions

Published on Tuesday, July 9th, 2013 by

If f(x) = 5x2 – 3x – 2, then f(-4) = ?

A. -70
B. -4
C. 70
D. 80
E. 90

 

 

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If f(x) = 5x2 – 3x – 2, then f(-4) = ?

A. -70
B. -4
C. 70
D. 80
E. 90

The correct answer is E. Plug in -4 in place of x in the equation to find f(-4).

5(-4)2 – 3(-4) – 2
5(16) + 12 – 2
80 + 12 – 2 = 90