Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 9 - Infinite Series - Review Exercises - Page 677: 59

Answer

Diverges

Work Step by Step

Let us suppose that a series $\Sigma a_n $ and $a_n=(-1)^n b_n$ or, $a_n=(-1)^{n+1} b_n$ with $b_n \geq 0$ for all $n$. We will apply the Alternating Series Test to compute when an infinite series converges, it must follow the following two conditions: a) $\lim\limits_{n \to \infty}b_n=0$ b) $b_n$ shows a decreasing sequence. Here, we have the $b_n=\dfrac{n}{n-3}$ $\lim\limits_{n \to \infty}b_n=\lim\limits_{n \to \infty} \dfrac{n}{n-3}=\lim\limits_{n \to \infty} \dfrac{1}{1-3/n}=1 \ne 0$ This means that the first condition for the Alternating Series Test fails. Thus, the given series diverges.
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