If f(x) = 2xsqrt(x-6), what is the value of (f^-1)(40)?

Answer 1

By inspection, f(10)=40, so f^-1(40) = 10

finding f^-1(x) is quite hard, since you have to solve a cubic.

http://www.wolframalpha.com/input/?i=inverse+2x%E2%88%9A(x-6)