Exercise 3.1-2: Incorrect use of the binomial theorem?

[ktbjob]

Hi.

Exercise 3.1-2 asks:

The solution begins by expanding using the binomial theorem, but b is a real-valued constant (e.g., b = pi would be a possible setting). I'm not sure if I misunderstood the question but this seems like an incorrect application of the expansion since b would have to be an integer.

Appreciate any replies to clarify this. Thanks!

[bissectra]

I guess this article might help you. Please take a look at the conditions for convergence of the binomial series.