Example 1. Let f(x) = x + 2vx -1. It is not difficult to see that f (x) is a one-to-one function. For example, it is routine to show that f (x) is increasing on its domain. (a) Find (f-)'(9) without finding an explicit formula for f-(a). (b) Confirm the above result by finding a formula for f-1(x) and taking the derivative