Algebra 2 Common Core

Published by Prentice Hall
ISBN 10: 0133186024
ISBN 13: 978-0-13318-602-4

Chapter 4 - Quadratic Functions and Equations - 4-8 Complex Numbers - Practice and Problem-Solving Exercises - Page 253: 31

Answer

$\dfrac{8}{13}+\dfrac{12}{13}i$

Work Step by Step

Multiplying both the numerator and the denominator of $ \dfrac{4}{2-3i} $ by the complex conjugate of the denominator, then \begin{align*}\require{cancel} & \dfrac{4}{2-3i}\cdot\dfrac{2+3i}{2+3i} \\\\&= \dfrac{4(2)+4(3i)}{(2-3i)(2+3i)} &\text{ (use Distributive Property)} \\\\&= \dfrac{4(2)+4(3i)}{(2)^2-(3i)^2} &\text{ (use $(a+b)(a-b)=a^2-b^2$)} \\\\&= \dfrac{8+12i}{4-9i^2} \\\\&= \dfrac{8+12i}{4-9(-1)} &\text{ (use $i^2=-1$)} \\\\&= \dfrac{8+12i}{4+9} \\\\&= \dfrac{8+12i}{13} \\\\&= \dfrac{8}{13}+\dfrac{12}{13}i .\end{align*} Hence, the simplified form of the given expression is $ \dfrac{8}{13}+\dfrac{12}{13}i $.
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