Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 10: Infinite Sequences and Series - Section 10.1 - Sequences - Exercises 10.1 - Page 571: 113

Answer

The sequence $a_n$ is not monotonic but bounded.

Work Step by Step

Consider $a_n=\dfrac{2^n 3^n}{n!}=\dfrac{6^n}{n!}$ for all $n \in N$ Also, $\lim\limits_{n \to \infty} a_n=\lim\limits_{n \to \infty}\dfrac{6^n}{n!}=0$ so, the sequence $a_n$ is bounded and converges to $0$ Now, $a_1= \dfrac{6^1}{1!}=6 \lt a_2=\dfrac{6^2}{2!}=\dfrac{36}{2 \cdot 1}=18$ However, $a_6= (\dfrac{6^6}{6!}) \gt a_7=(\dfrac{6^7}{7!})$ The sequence $a_n$ is not monotonic but bounded.
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