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: 30

Answer

$-\dfrac{3}{5}-\dfrac{4}{5}i$

Work Step by Step

Multiplying both the numerator and the denominator of $ \dfrac{i+2}{i-2} $ by the complex conjugate of the denominator, then \begin{align*}\require{cancel} & \dfrac{i+2}{i-2}\cdot\dfrac{i+2}{i+2} \\\\&= \dfrac{i(i)+i(2)+2(i)+2(2)}{(i-2)(i+2)} &\text{ (use FOIL)} \\\\&= \dfrac{i(i)+i(2)+2(i)+2(2)}{(i)^2-(2)^2} &\text{ (use $(a+b)(a-b)=a^2-b^2$)} \\\\&= \dfrac{i^2+2i+2i+4}{i^2-4} \\\\&= \dfrac{-1+2i+2i+4}{-1-4} &\text{ (use $i^2=-1$)} \\\\&= \dfrac{(-1+4)+(2i+2i)}{-1-4} \\\\&= \dfrac{3+4i}{-5} \\\\&= -\dfrac{3}{5}-\dfrac{4}{5}i .\end{align*} Hence, the simplified form of the given expression is $ -\dfrac{3}{5}-\dfrac{4}{5}i $.
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