Algebra and Trigonometry 10th Edition

Published by Cengage Learning
ISBN 10: 9781337271172
ISBN 13: 978-1-33727-117-2

Chapter 11 - 11.3 - Geometric Sequences and Series - 11.3 Exercises - Page 795: 38



Work Step by Step

$a_1=5$ $r=\frac{a_2}{a_1}=\frac{a_3}{a_2}$ $r=\frac{-40}{80}=\frac{20}{-40}=-\frac{1}{2}$ $a_n=a_1r^{n-1}$ $a_n=80(-\frac{1}{2})^{n-1}=80(-\frac{1}{2})^n(-\frac{1}{2})^{-1}=80(-\frac{1}{2})^n(-2)=-160(-\frac{1}{2})^n$
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