Answer
a) $g(x)$ has an inverse.
b) $g^{-1}(x)=\sqrt[3]{x}$
Work Step by Step
a) A function must be one-to-one to have an inverse. Out of the given function, only $g(x)=x^3$ is one-to-one, so it has an inverse.
b) The inverse of the cubic function is the third root function. Thus, we can write:
$g(x)=x^3$
$g^{-1}(x)=\sqrt[3]{x}$