Intro to Complex Analysis Using the results of Prob 2 find t

Intro to Complex Analysis Using the results of Prob. 2, find the circle of convergence of the following power series: Here is problem two. The results are stated in the question. Thank you! Assume for the power series we have lim j rightarrow infinity |a_j + 1/a_j| = L. Prove, by the ratio test, that the radius of convergence of the power series is given by R = 1/L.