Big Ideas Math - Algebra 1, A Common Core Curriculum

Published by Big Ideas Learning LLC
ISBN 10: 978-1-60840-838-2
ISBN 13: 978-1-60840-838-2

Chapter 6 - Exponential Functions and Sequences - 6.6 - Geometric Sequences - Exercises - Page 336: 25

Answer

The equation for the $n$th term is $a_n=2(4)^{n-1}$ and $a_6=2048$

Work Step by Step

The given series is $2,8,32,128,...$ First term $a_1=2$. Common ratio $r=\frac{8}{2}=4$. Equation for a geometric sequence is $\Rightarrow a_n=a_1r^{n-1}$ Substitute $2$ for $a_1$ and $4$ for $r$. $\Rightarrow a_n=2(4)^{n-1}$ Substitute $6$ for $n$. $\Rightarrow a_6=2(4)^{6-1}$ Simplify. $\Rightarrow a_6=2(4)^{5}$ $\Rightarrow a_6=2048$.
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