Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 8 - Sequences and Infinite Series - 8.4 The Divergence and Integral Tests - 8.4 Exercises - Page 639: 56

Answer

Convergent

Work Step by Step

Here, we have: $\Sigma_{k=1}^{\infty}\dfrac{2^k+3^k}{4^k}=\Sigma_{k=1}^{\infty} (\dfrac{1}{2})^k+\Sigma_{k=1}^{\infty} (\dfrac{3}{4})^k$ We will use the Geometric series formula $\Sigma_{n=0}^{\infty} ar^n=a+ar+ar^2+......=\dfrac{a}{1-r}$ Now, $\Sigma_{k=1}^{\infty}\dfrac{2^k+3^k}{4^k}=\Sigma_{k=1}^{\infty} (\dfrac{1}{2})^k+\Sigma_{k=1}^{\infty} (\dfrac{3}{4})^k$ or, $=\dfrac{1/2}{1-\dfrac{1}{2}}+\dfrac{3/4}{1-\dfrac{3}{4}}$ or, $=1+3$ or, $\Sigma_{k=1}^{\infty}\dfrac{2^k+3^k}{4^k}=4$ This implies that the series is convergent by using Geometric series formula.
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