University Calculus: Early Transcendentals (3rd Edition)

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

Chapter 9 - Section 9.1 - Sequences - Exercises - Page 489: 114

Answer

Monotonic (nondecreasing) and bounded from above.

Work Step by Step

A sequence is monotonic if it is nondecreasing or nonincreasing. \begin{align*} a_{n+1}-a_{n}&=(2-\displaystyle \frac{2}{n}-\frac{1}{2^{n}})-(2-\frac{2}{n+1}-\frac{1}{2^{n+1}}) \\ & =(\displaystyle \frac{2}{n+1}-\frac{2}{n})+(\frac{1}{2^{n+1}}-\frac{1}{2^{n}}) \\ & =\displaystyle \frac{2n-2(n+1)}{n+1}+\frac{1-2}{2^{n+1}} \\ & =\displaystyle \frac{-1}{n+1}+\frac{-1}{2^{n+1}} \\ & =-(\displaystyle \frac{1}{n+1}+\frac{1}{2^{n+1}})\leq 0 \\ a_{n+1}& \leq a_{n} \end{align*} Thus, $a_{n}$ is monotonic (nondecreasing). Also, $a_{n}=2-(\displaystyle \frac{2}{n}+\frac{1}{2^{n}})\lt 2$, so $\{a_{n}\}$ is bounded from above.
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