Answer
Domain: $[0,\infty)$, inverse:$f^{-1}(x)=x$.
Work Step by Step
According to the horizontal line test, we restrict the domain to $[0,\infty)$, (such that for every $y=f(x)$, there is a unique $x$, because we can only find the inverse of a one-to-one function) then $f^{-1}(x)$=x.$
