Question

The graph of which function is decreasing over the interval (–4, ∞)?

f(x) = (x + 4)2 + 4
f(x) = –(x + 4)2 + 4
f(x) = (x – 4)2 – 4
f(x) = –(x – 4)2 – 4

Answer 1

f(x) = –(x + 4)^2 + 4.

Reason: f'(x) = -2(x+4), which is negative for all x > -4, so the function is decreasing on (-4, ∞).