Question

11. If f(x)=4x-9, what is the equation for f^-1(x)?

Answer 1

f(x) = 4x - 9

let f(x) = y, this implies that  x = f⁻¹(y)

y = 4x - 9           Let us solve for x.

4x - 9 = y

4x = y + 9

x = (y + 9)/4

Recall that x = f⁻¹(y),

x = (y + 9)/4

f⁻¹(y) = (y + 9)/4

That means that for f⁻¹(x)

f⁻¹(x) = (x + 9)/4

Hope this explains it.