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: 57

Answer

Monotonic and Bounded

Work Step by Step

$a_n = (\frac{2}{3})^n $ $a_{n+1} = (\frac{2}{3})^{n+1} = \frac{2}{3} \times (\frac{2}{3})^n=\frac{2}{3} \times a_n $ Therefore, $a_{n+1}\lt a_n$ for all n. Or $a_1>a_2>...$ Hence the sequence is monotonic. Also note that each term of the sequence is less than $a_1$, i.e $ \frac{2}{3}$. So it is bounded from above by $\frac{2}{3}$ Since none of the numbers is negative, and $\lim\limits_{n \to \infty}(\frac{2}{3})^n =0$, the sequence is bounded from below by 0 Hence, the sequence is monotonic and bounded.
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