Algebra 1: Common Core (15th Edition)

Published by Prentice Hall
ISBN 10: 0133281140
ISBN 13: 978-0-13328-114-9

Chapter 8 - Polynomials and Factoring - 8-7 Factoring Special Cases - Practice and Problem-Solving Exercises - Page 527: 40


Error: $(9x)^{2}\neq 9x^{2}.$ The correct term is $3x, $ because $(3x)^{2}=9x^{2}.$ Correct factorization: $(3x+7)(3x-7)$

Work Step by Step

The square of 7 is 49, but the square of $9x$ is $81x^{2}$, not $9x^{2}.\\\\$ In applying the formula $a^{2}-b^{2}=(a+b)(a-b)$, here, $a=3x$, and $b=7$ So, the correct way to factor is $9x^{2}-49=(3x+7)(3x-7)$
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