Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 11 - Section 11.2 - Series - 11.2 Exercises - Page 716: 38

Answer

The series converges to $2 + \sqrt 2 $

Work Step by Step

We can rewrite the initial series as the geometric series $\sum\limits^{\infty}_{k=0} (\frac{1}{\sqrt 2})^k$ We can see that the first term is $ a = 1$ and the common ratio is $r = \frac{1}{\sqrt 2}$. Since $|r| \lt 1 $, we know the series converges and can use the formula $$\frac{a}{1-r} $$ to evaluate the sum $\frac{1}{1-\frac{1}{\sqrt 2}}$ = $\frac{\sqrt 2}{\sqrt 2 - 1} $ The sum can be simplified further by multiplying both the numerator and denominator by $1 + \sqrt 2 $ to get $\frac{ 2 +\sqrt 2}{(\sqrt 2)^2 - 1} $ = $\frac{ 2 +\sqrt 2}{1} $ = $2 + \sqrt 2 $
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