Answer
$396$
Work Step by Step
Since $18=20-2$ and $22=20+2$, then
$18 \times 22 = (20-2)(20+2)$.
Use the formula $(a-b)(a+b)=a^2-b^2$ with $a=20$ and $b=2$ to obtain:
$=20^2-2^2
\\=400-4
\\=396$
Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)
by Bittinger, Marvin L.; Ellenbogen, David J.; Johnson, Barbara L.
Published by
Pearson
ISBN 10:
0-32184-874-8
ISBN 13:
978-0-32184-874-1
Chapter 4 - Polynomials - 4.6 Special Products - 4.6 Exercise Set - Page 278: 113
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