Answer
$ f^{-1}(x)=x+9$
Work Step by Step
We are given the function, $f(x)=x-9$. First, we must replace $f(x)$ with y.
$y=x-9$
Next, interchange x and y.
$x=y-9$
Next, solve for y by adding 9 to both sides.
$y=x+9$
Finally, replace y with $f^{-1}(x)$.
$ f^{-1}(x)=x+9$
