Question

How do you find the value of df^-1/dx at x = f(a)?
f(x) = 5x + 10, a = 4

Answer 1

f(x) = 5x + 10
f'(x) = 5

at x = f(4), f(4) = 5(4) + 10

Answer 2

That's what I thought too, but the answer choices are 1/5 or 5 or 10 or 1/10

Answer 3

f'(x) = 5