Answer
$-10i$
Work Step by Step
Using $i^2=-1$, the expression $
(2-4i)(2-i)
$ simplifies to
\begin{array}{l}
2(2)+2(-i)-4i(2)-4i(-i)
\text{(use the FOIL method)}
\\=
4-2i-8i+4i^2
\\=
4-10i+4(-1)
\\=
-10i
.\end{array}
Intermediate Algebra (6th Edition)
by Martin-Gay, Elayn
Published by
Pearson
ISBN 10:
0321785045
ISBN 13:
978-0-32178-504-6
Chapter 7 - Section 7.7 - Complex Numbers - Exercise Set - Page 463: 60
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