Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 9 - Infinite Series - 9.1 Exercises - Page 593: 53

Answer

$\{a_{n}\}$ is bounded and monotonic

Work Step by Step

Bounded Sequences: 1. A sequence $\{a_{n}\}$ is bounded above when there is a real number $M$ such that $a_{n}\leq M$ for all $n$. The number $M$ is called an upper bound of the sequence. 2. A sequence $\{a_{n}\}$ is bounded below when there is a real number $N$ such that $N\leq a_{n}$ for all $n$. The number $N$ is called a lower bound of the sequence. 3. A sequence $\{a_{n}\}$ is bounded when it is bounded above and bounded below. ---------------------- The $\displaystyle \frac{1}{n}$ term is at most 1, never zero so the sequence is bounded with upper bound M=4 lower bound N=3 $\{a_{n}\}$ is bounded. Checking for monotony: $\displaystyle \frac{1}{n} > \frac{1}{n+1}\qquad \times(-1)$ $-\displaystyle \frac{1}{n} < -\frac{1}{n+1}\qquad +4$ $4-\displaystyle \frac{1}{n} < 4-\frac{1}{n+1}$ $a_{n} < a_{n+1}$ $\{a_{n}\}$ is monotonic (increasing, therefore nondecreasing) Graph (see below) confirms our conclusions.
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