Calculus: Early Transcendentals 9th Edition

Published by Cengage Learning
ISBN 10: 1337613924
ISBN 13: 978-1-33761-392-7

Chapter 11 - Section 11.2 - Series - 11.2 Exercises - Page 747: 8

Answer

The sequence appears divergent.

Work Step by Step

The sequence of the partial sums is given by $S_n=\sum_{k=1}^n(-1)^kk$. Substituting $n=1,2,\ldots,8$, we get the first eight terms of the sequence of the partial sums $S_1=-1$ $S_2=-1+2=1$ $S_3=-2$ $S_4=2$ $S_5=-3$ $S_6=3$ $S_7=-4$ $S_8=4$ Since $S_n$ contains a substring $-1,-2,-3,....$ going to $-\infty$ and a substring $1,2,3...$ going to $\infty$, the series appears divergent.
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