Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 12 Sequences and Series - 12.3 Analyze Geometric Sequences and Series - 12.3 Exercises - Skill Practice - Page 815: 53



Work Step by Step

We know that $S_{n}=a_1(\dfrac{r^{n}-1}{r-1})$ Common ratio $r=-4$ and $a_1= 1$ Now, $S_{11}=1[\dfrac{(-4)^{11}}{-4-1}]$ $S_{11}=\dfrac{(-4)^{11}-1}{-5}$ This gives: $S_{11}=\dfrac{4^{11}+1}{5}$ Hence, $S_{11}=\dfrac{4^{11}+1}{5}=838861$
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