Answer
$53$
Work Step by Step
RECALL:
(1) $(a+b)(a-b) = a^2-b^2$
(2) $i^2=-1$
Use rule (1) above with $a=2$ and $b=7i$ to obtain:
$=2^2 - (7i)^2
\\=4 - 49i^2$
Use rule (2) above to obtain:
$=4 - 49(-1)
\\=4-(-49)
\\=4+49
\\=53$
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: 46
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