You can not solve it for x in terms of y by using the standard methods.
Do you post all informations of this problem?
Let . show that f has an inverse and find .
If f(a) = 4, then a = 1. Since , f'(1)=3+3ln3
I was just curious to see what the inverse of f was. I assume that to show that f has an inverse means to solve for the inverse. Since this function is an increasing function, it has an inverse.