University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 9 - Section 9.4 - Comparison Tests - Exercises - Page 509: 43

Answer

Converges

Work Step by Step

Since, we have $a_n=\Sigma_{n=2}^\infty \dfrac{1}{n !}=\Sigma_{n=2}^\infty \dfrac{1}{n (n-1)(n-2)(n-3)!}$ and $a_n \lt \Sigma_{n=2}^\infty \dfrac{1}{n (n-1)!} \lt \Sigma_{n=2}^\infty \dfrac{1}{(n-1)(n-1)}=\Sigma_{n=1}^\infty \dfrac{1}{n^2}$ we can see that $\Sigma_{n=2}^\infty \dfrac{1}{n !} \lt \Sigma_{n=1}^\infty \dfrac{1}{n^2}$ which is a p-series with $p=2 \gt 1$ and thus, convergent. Hence, the given series also converges.
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