Let f (x) = 2x+2. solve f^-1 (x) when x=4

F⁻¹ (x) is the notation for the inverse of an equation, so you just need to find the inverse equation. that's found by swapping your x and y variables:

f (x) = 2x + 2 ... replace f (x) with y

y = 2x + 2 ... swap x and y variables

x = 2y + 2 ... solve for y

x = 2y + 2 ... subtract 2

x - 2 = 2y ... divide by 2

(x - 2) / 2 = y

so, f⁻¹ (x) = (x - 2) / 2 ... now you need to solve that for when x = 4. plug it in:

f⁻¹ (x) = (4 - 2) / 2 ... simplify the top of the fraction

f⁻¹ (x) = 2/2

f⁻¹ (x) = 1 is your answer.