Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 8 - Sequences and Infinite Series - 8.4 The Divergence and Integral Tests - 8.4 Exercises - Page 638: 34

Answer

\[\text{The series diverges}\]

Work Step by Step

\[\begin{align} & \sum\limits_{k=1}^{\infty }{\frac{1}{\sqrt[3]{27{{k}^{2}}}}} \\ & \text{Rewrite the series} \\ & \sum\limits_{k=1}^{\infty }{\frac{1}{\sqrt[3]{27{{k}^{2}}}}}=\sum\limits_{k=1}^{\infty }{\frac{1}{3\sqrt[3]{{{k}^{2}}}}} \\ & \text{ }=\frac{1}{3}\sum\limits_{k=1}^{\infty }{\frac{1}{{{\left( {{k}^{2}} \right)}^{1/3}}}} \\ & \text{ }=\frac{1}{3}\sum\limits_{k=1}^{\infty }{\frac{1}{{{k}^{2/3}}}} \\ & \text{Using the p-series test }\left( \text{Theorem 8}\text{.11}\text{, page 632} \right) \\ & \text{The }p\text{-series }\sum\limits_{k=1}^{\infty }{\frac{1}{{{k}^{p}}}\text{ converges for }p>1\text{ and diverges for }p\le 1} \\ & \text{Comparing} \\ & \underbrace{\sum\limits_{k=1}^{\infty }{\frac{1}{{{k}^{2/3}}}}}_{\sum\limits_{k=1}^{\infty }{\frac{1}{{{k}^{p}}}}}\Rightarrow p=\frac{2}{3}<1 \\ & p<1,\text{ then the series diverges} \\ \end{align}\]
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