# Let f(x) = 2x + 2, how do you solve f^-1(x) when x = 4?

Exchange x and y and the inverse is $x = 2 y + 2$
$x - 2 = 2 y \implies y = \frac{x}{2} - 1 = {f}^{-} 1 \left(x\right)$
${f}^{-} 1 \left(4\right) = \frac{4}{2} - 1$