Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 5 - Number Theory and the Real Number System - Chapter Summary, Review, and Test - Review Exercises - Page 337: 142

Answer

The \[{{n}^{th}}\] term of given geometric sequence is \[{{a}_{n}}={{10}^{3-n}}\]. The eighth term of the geometric sequence is\[\frac{1}{100,000}\].

Work Step by Step

Here, the first term is \[{{a}_{1}}=100\] and the ratio is, \[\begin{align} & r=\frac{{{a}_{2}}}{{{a}_{1}}} \\ & =\frac{10}{100} \\ & =\frac{1}{10} \end{align}\] Hence, the general term for the given geometric sequence is \[\begin{align} & {{a}_{n}}={{a}_{1}}{{r}^{n-1}} \\ & \,\,\,\,\,\,=100{{\left( \frac{1}{10} \right)}^{n-1}}\,\, \\ \end{align}\] To find the eighth term put \[n=8\] in the above formula, to get: \[\begin{align} & {{a}_{8}}={{a}_{1}}{{r}^{8-1}} \\ & =100\cdot {{\left( \frac{1}{10} \right)}^{7}} \\ & =100\cdot \frac{1}{10000000} \\ & =\frac{1}{100000} \end{align}\] The \[{{n}^{th}}\] term of given geometric sequence is \[{{a}_{n}}={{10}^{3-n}}\]. The eighth term of the geometric sequence is\[\frac{1}{100,000}\].
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