Question

Given the following functions f(x) and g(x), solve (f+g)(3) and select the correct answer below.

F(x)=2x+21
G(x)=x-21

A. -27
B. -21
C. 6
D. 48

Answer 1

f(x) = 2x + 21
g(x) = x - 21

(f + g)(x) = f(x) + g(x) = (2x + 21) + (x - 21) = 2x + 21 + x - 21 = 3x

subtitute x=3:

(f + g)(3) = 3 · 3 = 9