Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 9 - Infinite Series - 9.1 Sequences - Exercises Set 9.1 - Page 606: 22

Answer

First five terms are: $-1; 0; (\dfrac{1}{3})^3; (\dfrac{2}{4})^4; (\dfrac{3}{5})^5$ Converges to $e^{-2}$.

Work Step by Step

Plugging $n = {1,2,3,4,5}$ in $(1-\dfrac{2}{n})^n$. $\implies n=1$: $(1-\dfrac{2}{1})^1=-1$ $\implies n=2$: $(1-\dfrac{2}{2})^2=0$ $\implies n=3$: $(1-\dfrac{2}{3})^3=(\dfrac{1}{3})^3$ $\implies n=4$: $(1-\dfrac{2}{4})^4=(\dfrac{2}{4})^4$ $\implies n=5$: $(1-\dfrac{2}{5})^5=(\dfrac{3}{5})^5$ We see that $l=\lim\limits_{n \to \infty} (1-\dfrac{2}{n})^n$ or, $\ln l=\lim\limits_{n \to \infty} x \ln (1-\dfrac{2}{n})\\=\lim\limits_{n \to \infty} \dfrac{-2n}{n-2}\\=\lim\limits_{n \to \infty} \dfrac{-2}{1-2/n}$ or, $\ln l=-2$ or, $ l=e^{-2}$ Therefore, the given series converges to $e^{-2}$.
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