If z is a real number, then is defined recursively for non-negative integers

And, for

.

If z is a positive real number, and b a natural number, then we may define the positive bth root

to be the positive real number y such that

.

You may assume that a positive real number always has a positive bth root.

a) Given a positive real number z, is it possible for there to be two different positive bth roots of z? Justify your answer briefly.

Any help would be greatly appreciated :)