Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 11 - Further Topics in Algebra - 11.3 Geometric Sequences and Series - 11.3 Exercises: 28

Answer

$r=-2;a_{1}=4$

Work Step by Step

$\dfrac {a_{m}}{a_{n}}=r^{m-n}\Rightarrow \dfrac {a_{7}}{a_{2}}=r^{5}\Rightarrow \dfrac {256}{-8}=r^{5}=-32\Rightarrow r=-2;a_{2}=a_{1}xr\Rightarrow -8=a_{1}\times \left( -2\right) \Rightarrow a_{1}=4$
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