Find the inverse of the cubic function What is the resulting equation when $y=x^3 + 2x^2$ is reflected in the line $y=x$ ? 
I have tried and tried and am unable to come up with the answer. 
The furthest I was able to get without making any mistakes or getting confused was $x= y^3 + 2y^2$. What am I supposed to do after that step? 

If you plot the equation $y = x^3 + 2y^2$, you'll find that it fails the horizontal line test, and thus that it is not a one-to-one function and its inverse is not a function. So user130558's answer must be wrong since it doesn't include any $\pm$ signs.
Unless your textbook/teacher tells you otherwise, they probably expect you to simply give the result $x = y^3 + 2y^2$ that you already got.
