Proof: Invertibility implies a unique solution to f(x)=y

In mathematics, an inverse function is a function that "reverses" another function: if the function f applied to an input x gives a result of y, then applying its inverse function g to y gives the result x, and vice versa. i.e., f(x) = yif and only if g(y) = x. Referred from Wikipedia.

    Proof: Invertibility implies a unique solution to f(x)=y: Proof: Invertibility implies a unique solution to f(x)=y for all y in co-domain of f.