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: 45



Work Step by Step

$a_n=a_1r^{n-1}$ $a_4=a_1r^3$ $a_7=a_1r^6$ $\frac{a_7}{a_4}=\frac{a_1r^6}{a_1r^3}$ $\frac{\frac{2}{3}}{-18}=r^3$ $r^3=-\frac{1}{27}$ $r=\sqrt[3] {-\frac{1}{27}}=-\frac{1}{3}$ $\frac{a_7}{a_6}=r$ $a_6=\frac{a_7}{r}=\frac{\frac{2}{3}}{-\frac{1}{3}}=-2$
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