Question

Suppose that f'(c) = 0 where f is a differentiable function. Then, the rate at which f changes at x=c is

A) infinity
B) 0
C) f(c)
D) c

Answer 1

0
Since every time you substitute with x will get zero

Answer 2

Well... to find the rate at which the function changes, we differentiate it. Now if we want to know at what rate the function is changing we evaluate it at a number, c.

They gave us.
f'(c) = 0