Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 11 - Infinite Sequences and Series - 11.4 The Comparison Tests - 11.4 Exercises - Page 771: 11

Answer

Converges

Work Step by Step

The Comparison Test states that the p-series $\sum_{n=1}^{\infty}\frac{1}{n^{p}}$ is convergent if $p\gt 1$ and divergent if $p\leq 1$. Using the Comparison Test , the series is less than $\Sigma _{k=1}^{\infty}\frac{\sqrt[3] k}{\sqrt{ k^{3}}} $ because the denominator of the original series is always slightly larger than the series on the right. Therefore, $\Sigma _{k=1}^{\infty}\frac{\sqrt[3] k}{\sqrt{ k^{3}+4k+3}} \leq \Sigma _{k=1}^{\infty}\frac{\sqrt[3] k}{\sqrt{ k^{3}}} $ Re-arranging the exponents . $\Sigma _{k=1}^{\infty}\frac{\sqrt[3] k}{\sqrt{ k^{3}+4k+3}} \leq \Sigma _{k=1}^{\infty}\frac{k^{1/3}}{k^{3/2}} $ $\Sigma _{k=1}^{\infty}\frac{\sqrt[3] k}{\sqrt{ k^{3}+4k+3}} \leq \Sigma _{k=1}^{\infty}\frac{1}{k^{1/6}} $ We find that the series on the right side is a p-series with $p \gt 1$ , so the series on the right side converges and therefore, the series on the left converges.
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