Complex Analysis: Theory and Applications · Problem 4.3.4

Elementary Functions — Howell & Matthews

Mathematics — Complex Analysis · ratio-test-convergence

Problem

Use the ratio test to show that the following series converge. ((a)) ∑n=0∞(1+i2)n\displaystyle\sum_{n=0}^{\infty} \left(\frac{1+i}{2}\right)^n. ((b)) ∑n=1∞(1+i)nn2n\displaystyle\sum_{n=1}^{\infty} \frac{(1+i)^n}{n2^n}. ((c)) ∑n=1∞(1+i)nn!\displaystyle\sum_{n=1}^{\infty} \frac{(1+i)^n}{n!}. ((d)) ∑n=0∞(1+i)2n(2n+1)!\displaystyle\sum_{n=0}^{\infty} \frac{(1+i)^{2n}}{(2n+1)!}.

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