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 - 5.7 Arithmetic and Geometric Sequences - Exercise Set 5.7 - Page 332: 149

Answer

The provided statement is true.

Work Step by Step

It is known the nth term of an arithmetic sequence is; \[{{a}_{n}}=a+\left( n-1 \right)d\] Where a is first term, n is term, and d is common difference. \[\begin{align} & a=5 \\ & {{a}_{3}}=-3 \end{align}\] So, \[\begin{align} & -3=5+\left( 3-1 \right)d \\ & 2d=-3-5 \\ & d=\frac{-8}{2} \\ & =-4 \end{align}\] Now, the fourth term is; \[\begin{align} & {{a}_{4}}=5+\left( 4-1 \right)\left( -4 \right) \\ & =5+\left( 3 \right)\left( -4 \right) \\ & =5-12 \\ & =-7 \end{align}\] Hence, the fourth term is\[-7\]. Hence, the provided statement is true.
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