Answer
$20$
Work Step by Step
RECALL:
(1) $(a+b)(a-b) = a^2-b^2$
(2) $i^2=-1$
Use rule (1) above with $a=-4$ and $b=2i$ to obtain:
$=(-4)^2 - (2i)^2
\\=16 - 4i^2$
Use rule (2) above to obtain:
$=16 - 4(-1)
\\=16-(-4)
\\=16+4
\\=20$
Intermediate Algebra for College Students (7th Edition)
by Blitzer, Robert F.
Published by
Pearson
ISBN 10:
0-13417-894-7
ISBN 13:
978-0-13417-894-3
Chapter 7 - Section 7.7 - Complex Numbers - Exercise Set - Page 570: 48
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