The function is
.
Find an equation for the inverse function.
\Let
and solve for
in terms of
.
Let
.
.
Differentiate on each side with respect to
.
\
.
.
, which is always positive for
so the function
is strictly increasing on its domain.
The domain of
is
.
There is no negative terms so the function
is monotonic.
Therefore
is monotonic and it has an inverse function.
Inverse function of
exists because the function
is monotonic.