Function problems

[austere fractal]

Express the inverse function (f-1) in the form f-1(x)=

[pearl turret]

Something tells me you forgot to include the rest of the question

However, since the graph of the inverse $f^{-1}$ is the reflection of the graph of the original function $f$ over $y=x$, assuming $y=f(x)$, you can set $f(y)=x$ and solve again for $y$.