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 750: 23

Answer

Convergent

Work Step by Step

Use Limit Comparison Test with $a_{n}=\frac{5+2n}{{(1+n^{2})^{2}}}$ and $b_{n}=\frac{1}{n^{3}}$ $\lim\limits_{n \to \infty}\frac{a_{n}}{b_{n}}=\lim\limits_{n \to \infty}\frac{n^{3}(5+2n)}{(1+n^{2})^{2}}$ $=\lim\limits_{n \to \infty}\frac{5n^{3}+2n^{4}}{(1+n^{2})^{2}}$ $=\lim\limits_{n \to \infty}\frac{\frac{5}{n}+2}{(\frac{1}{n^{2}}+1)^{2}}$ $=2\gt 0$ $\Sigma_{n=1}^{\infty}\frac{1}{n^{3}}$ is convergent because a $p-$series with $p=3 \gt 1$ is convergent, thus the series $\Sigma_{n=1}^{\infty}\frac{5+2n}{{(1+n^{2})^{2}}}$ also converges.
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