Intermediate Algebra for College Students (7th Edition)

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: 53

Answer

$21 - 20i$

Work Step by Step

RECALL: (1) $(a-b)^2 = a^2 - 2ab + b^2$ (2) $i^2=-1$ Use rule (1) above with $a=5$ and $b=2i$ to obtain: $=5^2 - 2(5)(2i) + (2i)^2 \\=25 - 20i + 4i^2$ Use rule (2) above to obtain: $=25 - 20i + 4(-1) \\=25 - 20i+(-4) \\=21 - 20i$
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