You can put this solution on YOUR website! I have plotted both curves for you. I have done this to show you that picking certain y-values gives you multiple values of x. This contravenes the one basic requirement of any function...it must NOT be one-to-many.
Hence, strictly, neither of these functions have inverse functions. Now, you could get round that by narrowing the domain of the functions, such that the one-to-many region of the curves is not included, but forgeet that: just say:
There is no inverse because the function is ONE-TO-MANY. If your teacher argues, then pass them over to me here and i shall argue with them.