Calculus: Early Transcendentals (2nd Edition)

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

Chapter 8 - Sequences and Infinite Series - Review Exercises - Page 659: 31

Answer

Converges

Work Step by Step

We have: $a_k=\dfrac{\sqrt[k] k}{k^3}$ and $b_k=\dfrac{1}{k^3}$ Now, we need to apply the limit comparison test. $L=\lim\limits_{k \to \infty}\dfrac{a_k}{b_k}\\=\lim\limits_{k \to \infty}\dfrac{\dfrac{\sqrt[k] k}{k^3}}{1/k^{3}}\\=\lim\limits_{k \to \infty} \sqrt[k] k\\=1$ We see that $0 \lt \lim\limits_{k \to \infty}\dfrac{a_k}{b_k} \lt \infty$ and the series $\Sigma b_k$ convergent p-series with $p=3$.Therefore, the given series converges by the limit comparison test.
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