Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 11 - Sequences; Induction; the Binomial Theorem - Chapter Test - Page 860: 3

Answer

$$\dfrac{61}{36}$$

Work Step by Step

We simplify the summation by plugging in the values from $1$ to $3$ as follows: $$\displaystyle \sum_{k=1}^{3} (-1)^{k+1}\frac{k+1}{k^2}\\=(-1)^{1+1}\ \frac{1+1}{1^2}+(-1)^{2+1}\ \frac{2+1}{2^2}+(-1)^{3+1}\ \frac{3+1}{3^2}\\=(-1)^{2}\times \frac{2}{1}+(-1)^{3}\times \frac{3}{4}+(-1)^{4}\times \frac{4}{9}\\=\frac{61}{36}$$
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