Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 9 - Infinite Series - 9.5 The Comparison, Ratio, And Root Tests - Exercises Set 9.5 - Page 636: 16

Answer

Inconclusive

Work Step by Step

Apply the ratio test. Therefore, $ L=\lim\limits_{k \to \infty} |\dfrac{a_{k+1}}{a_k}|=\lim\limits_{k \to \infty} \dfrac{(k^2+1)}{k^2+2k+2} \times \dfrac{k^2+1}{k} \\=\lim\limits_{k \to \infty} \dfrac{(k+1)}{k^2+2k+2} \times \lim\limits_{k \to \infty} \dfrac{k^2+1}{k} \\=\lim\limits_{k \to \infty} \dfrac{1+1/k^2}{1+2/k+2/k^2} \times \lim\limits_{k \to \infty} (1+\dfrac{1}{k}) \\=\dfrac{1+0}{1+0+0} \times (1+0) \\=1$ So, we can conclude that the given series is inconclusive by the ratio test.
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