Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 11 - Sequences; Induction; the Binomial Theorem - Section 11.3 Geometric Sequences; Geometric Series - 11.3 Assess Your Understanding - Page 844: 15

Answer

The sequence is geometric with a common ratio of $\sqrt[3]{2}$.

Work Step by Step

We need to substitute $1, 2, 3,$ and $4$ for $n$ into the given equation to find the first four terms. $e_1=2^{1/3}=2^{1/3}=\sqrt[3]{2} \\ e_2=2^{2/3}=\sqrt[3]{2^2} = \sqrt[3]{4} \\ e_3=2^{3/3}=2 \\ e_4=2^{4/3}=\sqrt[3]{2^4} = \sqrt[3]{2^3(2)}=2\sqrt[3]{2}$ Our aim is to check if the sequence is geometric and then compute the ratio of each successive pairs. $\dfrac{a_2}{a_1}=\dfrac{\sqrt[3]{4}}{\sqrt[3]{2}} =\sqrt[3]{2}$ $\dfrac{a_3}{a_2}=\dfrac{2}{\sqrt[3]{4}}=\dfrac{2 \cdot \sqrt[3]{2}}{\sqrt[3]{4} \cdot \sqrt[3]{2}}=\dfrac{2\sqrt[3]{2}}{2}=\sqrt[3]{2}$ $\dfrac{a_4}{a_3}=\dfrac{2\sqrt[3]{2}}{2}=\sqrt[3]{2}$ We can see that the common ratios are the same; thus the sequence is geometric with a common ratio of $\sqrt[3]{2}$.
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