This page is entirely written for MATH V01 Assignment 7 question 3 (b).

The key to approach this problem is to realize that the series is absolutely convergent and the absolute convergence implies that the original series is also convergent. First, implement the ratio test on the series to find the interval of x so that the series absolutely converges. Then, carefully state that the original series also converges in the interval using the argument above. The calculation is fairly straightforward. So, it should not take too much time; however, patience is required to lead the conclusion.