University Calculus: Early Transcendentals (3rd Edition)

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

Chapter 9 - Section 9.3 - The Integral Test - Exercises - Page 504: 36

Answer

Convergent

Work Step by Step

Since, we have $\lim\limits_{x \to \infty} \int_1^\infty\dfrac{2}{e^x(1+e^x)}$ Suppose $e^x= p \implies dx=\dfrac{1}{p} dp$ or, $=\lim\limits_{a \to \infty} [\dfrac{2}{p}-\dfrac{2}{p+1}]_e^\infty$ or, $=\lim\limits_{a \to \infty} [2(\dfrac{a}{a+1}-2(\dfrac{e}{e+1})]$ or, $ =-2 \ln (\dfrac{e}{e+1}) \approx 0.63$ Hence, the series is Convergent by the Integral Test
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