Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 8 - Radical Functions - 8.5 Complex Numbers - 8.5 Exercises - Page 663: 66

Answer

$\frac{61}{34}-\frac{11}{34} i$

Work Step by Step

Rewrite the given expression, and solve the latter. \begin{equation} \frac{-7-8 i}{-3-5 i}= \frac{7+8 i}{3+5 i}. \end{equation} Multiply both numerator and denominator by the conjugate of the denominator and simplify. \begin{equation} \begin{aligned} \frac{7+8 i}{3+5 i}&=\frac{7+8 i}{3+5 i}\cdot \frac{(3-5 i)}{(3-5 i)}\\ & =\frac{7(3-5 i)+8i(3-5 i)}{9+25}\\ &=\frac{21-35i+24i+40}{34}\\ &= \frac{61}{34}-\frac{11}{34} i. \end{aligned} \end{equation} We got \begin{equation} \frac{-7-8 i}{-3-5 i}= \frac{61}{34}-\frac{11}{34} i. \end{equation}
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