Let y=f(x)=(x-2)2, which has range [0,∞), x-2=√y, x=2+√y. Let x=g(y)=2+√y, then g(x)=2+√x, which has domain [0,∞) and range [2,∞) and g(x) is the inverse of f(x). f(g(x))=(g(x)-2)2=x, and g(f(x))=2+√f(x)=2+x-2=x, which is the requirement for an inverse.