Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 1 - Equations and Inequalities - 1.3 Complex Numbers - 1.3 Exercises - Page 113: 106

Answer

$-2-i$ satisfies the equation.

Work Step by Step

$ x^{2}+4x+5=0\qquad$...substitute $x$ for $-2-i$. $(-2-i)^{2}+4(-2-i)+5=0\qquad$...Apply the Perfect Square Formula: $(a-b)^{2}=a^{2}-2ab+b^{2},\ a=-2,\ b=i$ $(-2)^{2}-2(-2)i+i^{2}+4(-2-i)+5=0$ $ 4+2\cdot 2i+i^{2}+4(-2-i)+5=0\qquad$...Apply imaginary number rule: $\quad i^{2}=-1$ $ 4+4i-1+4(-2-i)+5=0\qquad$...Simplify. $ 8+4i+4(-2-i)=0\qquad$...Apply the distributive property: $\quad a(b-c)=ab-ac$ $ 8+4i+4(-2)-4i=0\qquad$...Simplify. $8-8+4i-4i=0$ $0=0$
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