Multivariable Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 0-53849-787-4
ISBN 13: 978-0-53849-787-9

Chapter 11 - Infinite Sequences and Series - 11.4 Exercises - Page 751: 43

Answer

$\Sigma a_{n}$ is divergent.

Work Step by Step

Given that $a_{n}\gt 0$ , we can apply the limit comparison test with $b_{n}=\frac{1}{n}$ Since, $\Sigma_{n=0}^{\infty}b_{n}=\Sigma_{n=0}^{\infty}\frac{1}{n}$ diverges If $\lim\limits_{n\to \infty}\frac{a_{n}}{b_{n}}\ne 0$ Then according to the limit comparison test, $\Sigma_{n=0}^{\infty}a_{n}$ will also diverge. $\lim\limits_{n\to \infty}\frac{a_{n}}{b_{n}}=\lim\limits_{n\to \infty}\frac{a_{n}}{1/n}=\lim\limits_{n\to \infty}na_{n}$ $\ne 0$ Hence, $\Sigma a_{n}$ is divergent.
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