Answer
$159,999$
Work Step by Step
$399\cdot 401=$
...write as a product of a sum and a difference.
$=(400+1)(400-1)$
...use $(a+b)(a-b)=a^{2}-b^{2}$.
$=400^{2}-1^{2}$
...simplify powers.
$=160,000-1$
...simplify.
$=159,999$
Algebra 1: Common Core (15th Edition)
by Charles, Randall I.
Published by
Prentice Hall
ISBN 10:
0133281140
ISBN 13:
978-0-13328-114-9
Chapter 8 - Polynomials and Factoring - 8-4 Multiplying Soecial Cases - Practice and Problem-Solving Exercises - Page 508: 34
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