We are given that `f:RR->RR` where `f(x)=x^2` and we are asked to find the inverse `f^(-1)(x)` :
The inverse does not exist.
(1) The graph of `f(x)` fails the horizontal line test -- e.g. the line y=4 intersects the graph at x=2 and x=-2, therefore the inverse is not a function
(2) `f(x)` is not injective (1-1 or one-to-one) as f(2)=f(-2)=4
(3) If you try to solve for the inverse, you end up with domain restrictions:
The inverse relation is the parabola x=y^2, which is not a function (it's graph fails the vertical line test, etc...)
The graph of the function (black) and the inverse relation (red):