Elementary Algebra

Published by Cengage Learning
ISBN 10: 1285194055
ISBN 13: 978-1-28519-405-9

Chapter 11 - Additional Topics - 11.4 - Complex Numbers - Problem Set 11.4: 53

Answer

$5+0i$

Work Step by Step

First of all, recall that $i=\sqrt{-1}$, so $i^{2}=-1$ Also, since $(a+b)(a-b)=a^{2}-b^{2}$, we obtain: $(-2-i)(-2+i)$ =$(-2)^{2}-(i)^{2}$ =$4-i^{2}$ =$4-(-1)$ =$4+1$ =$5$ Since we have to write the answer in the form $(a+bi)$, we write: $5=5+0i$
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