Question

If f(x) and f⁻¹(x) are inverse functions of each other and f(x)=2x+5, what is f⁻¹(8)?

-1
3/2
41/8
23

Answer 1

3/2.

Explanation:

f(x)=2x+5 Finding the inverse:

y = 2x + 5

2x = y - 5

x = (y - 5)/2

So the inverse f-1(x) = (x - 5)/2

and f-1(8) = (8-5)/2

= 3/2.