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 617: 52

Answer

False

Work Step by Step

We are given that $a_n \leq b_n+ c_n$ and the series $a_n$ diverges. In order to determine the correct statement, we need to consider $a_n=b_n=\dfrac{1}{n}$ and $c_n=\dfrac{1}{n^2}$ We can notice that $\dfrac{1}{n}\leq \dfrac{1}{n}+\dfrac{1}{n^2}$ because $\dfrac{1}{n^2} \gt 0$ Also, by the p-series test ($\Sigma_{n=1}^{\infty} \dfrac{1}{n^p}\implies p \gt 1;$ series converges), so the series $\Sigma c_n$ converges because $p=2 \gt 1$. Therefore, we can conclude that the series $\Sigma a_n$ diverges but both the series $\Sigma b_n$ and $\Sigma c_n$ converges; not diverges. Thus, the given statement is false.
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