Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 12 - Section 12.3 - Geometric Sequences - 12.3 Exercises - Page 866: 97

Answer

3 m

Work Step by Step

Let $a_{n}$ be the height the ball after the nth bounce. Given: $a_{0}=1$ and $a_{n}=\displaystyle \frac{1}{2}a_{n-1}$. $a_{1}=\displaystyle \frac{1}{2}, $ $a_{2}=\displaystyle \frac{1}{2}(\frac{1}{2})=(\frac{1}{2})^{2}$ $a_{3}=\displaystyle \frac{1}{2}(\frac{1}{2})^{2}=(\frac{1}{2})^{3}$ $...$ $a_{n}=(\displaystyle \frac{1}{2})^{n}$ The total distance traveled = $a_{0}+$ $+2a_{1}\quad$ ($a_{1}$ up, $a_{1}$ down), $+2a_{2}\quad$ ($a_{2}$ up, $a_{2}$ down), $+2a_{3}\quad$ ($a_{3}$ up, $a_{3}$ down), $+...$ $=1+2(\displaystyle \frac{1}{2})+2(\frac{1}{2})^{2}+2(\frac{1}{2})^{3}+2(\frac{1}{2})^{4}+\cdots$ $=1+(1+\displaystyle \frac{1}{2}+(\frac{1}{2})^{2}+(\frac{1}{2})^{3}+\cdots)$ $=1+\displaystyle \sum_{k=1}^{\infty}(\frac{1}{2})^{k-1}\qquad $... geometric series, ... a=1, $r=\displaystyle \frac{1}{2} < 1$. so it converges to $\displaystyle \frac{a}{1-r}$ ... $=1+\displaystyle \frac{1}{1-\frac{1}{2}}$ $=1+\displaystyle \frac{1}{\frac{1}{2}}=1+2$ $=3$
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