Which values of x will cause the square root expression to be undefined?
If f(x) = y, then switch the x and the y in f(x). Solve for y.
Switch the domain and range of f(x).
Substitute the equation g(x) that you found in part (b) for x in f(x).
See part (d). What relationship do f(x) and g(x) have with each other? (What is the relationship between two inverses?)