Calculus 10th Edition

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

Chapter 9 - Infinite Series - 9.4 Exercises - Page 616: 23

Answer

Divergent Using the Limit Comparison Test

Work Step by Step

Given $$\sum_{n=1}^{\infty} \frac{\sqrt[3]{n}}{n}$$ Use the Limit Comparison Test with $a_n = \dfrac{\sqrt[3]{n}}{n}$ and $b_n=\dfrac{1}{n^{2/3}}$ \begin{align*} \lim _{n \rightarrow \infty} \frac{a_{n}}{b_{n}}&=\lim _{n \rightarrow \infty} \frac{n^{2/3}n^{1/3}}{n }\\ &=\lim _{n \rightarrow \infty} \frac{n }{n }\\ &=1 \end{align*} Since $\displaystyle \sum_{n=1}^{\infty} \frac{1}{n^{2/3}}$ is divergent $( p-\text{series} \ p<1)$ , then $\displaystyle\sum_{n=1}^{\infty} \frac{\sqrt[3]{n}}{n}$ is also divergent
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