College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 8, Sequences and Series - Chapter 8 Review - Exercises - Page 640: 44

Answer

$(1^2)(2^1)+(2^2)(2^2)+(3^2)(2^3)+(4^2)(2^4)+(5^2)(2^5)+(6^2)(2^6)+(7^2)(2^7)+(8^2)(2^8)+(9^2)(2^9)+(10^2)(2^{10})$

Work Step by Step

We rewrite the given sum by expanding it: in each term $n^22^n$ substitute the value of $n$, where $n=1,2,3,\dots,10$: $$\begin{align*} \sum_{n=1}^{10}n^22^n&=(1^2)(2^1)+(2^2)(2^2)+(3^2)(2^3)+(4^2)(2^4)+(5^2)(2^5)+(6^2)(2^6)+(7^2)(2^7)+(8^2)(2^8)+(9^2)(2^9)+(10^2)(2^{10}). \end{align*}$$
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