Question 963342
{{{y=3x^2}}}
Interchange x and y and solve for y, that's the inverse.
{{{x=3y^2}}}
{{{x/3=y^2}}}
{{{y=sqrt(x/3)}}} and {{{y=-sqrt(x/3)}}}

{{{f^(-1)(x)=sqrt(x/3)}}} and {{{f^(-1)(x)=-sqrt(x/3)}}}