Inversing a cubic function

Question

I'm needing to inverse a complex cubic function f(x)=(15-2x)(20-2x)(x).

 

Is there a way to do this without diving into calculus?

Answer 1

This FUNCTION has three zeros, and it's a function that does not pass the HORIZONTAL LINE TEST and consequently has no Inverse.  (The graph comes up from negative values, crosses x axis at 0, 7.5 and 10, and then continues on upward.)