Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Appendix A - Review - A.7 Complex Numbers; Quadratic Equations in the Complex Number System - A.7 Assess Your Understanding - Page A60: 25

Answer

$\dfrac{6}{5}+\dfrac{8i}{5}$

Work Step by Step

Multiply the numerator and the denominator by the conjugate of $3-4i$. $\dfrac{10}{3-4i}=\dfrac{10}{3-4i}\cdot \dfrac{3+4i}{3+4i}$ Use special formula $(a+b)(a-b)=a^2-b^2$ in the denominator. $=\dfrac{10(3+4i)}{(3)^2-(4i)^2}$ $=\dfrac{10(3+4i)}{9-16i^2}$ Use $i^2=-1$. $=\dfrac{10(3+4i)}{9-16(-1)}$ Simplify. $\require{cancel} =\dfrac{10(3+4i)}{9+16}\\ =\dfrac{10(3+4i)}{25}\\ =\dfrac{\cancel{10}^2(3+4i)}{\cancel{25}^5}\\ =\dfrac{2(3+4i)}{5}$ Use distributive property in the numerator. $=\dfrac{6+8i}{5}$ $=\dfrac{6}{5}+\dfrac{8i}{5}$ Hence, the solution in the standard form is $\dfrac{6}{5}+\dfrac{8i}{5}$.
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