Question 15 from "(I'm Overwhelmed) Algebra Progress Quiz #4 (Version 2)"

GRE GRE Quant Problem Solving
1

https://www.gregmat.com/quizzes/quiz/im-overwhelmed-algebra-progress-quiz-4-version-2 (Question 15)

Why is the answer 140 instead of -140? If the equation becomes (x+5)squared - 28. Where a=5 and b=-28. then 5 X -28 = -140. The solution video and quiz show 5 X 28 = 140, but the b value is negative?

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It’s because the negative is already factored into the functional form. It specifically says (x+a)^2 - b so b would only be -28 if it was (x+5)^2 + 28 but since it’s (x+5)^2 - 28 b is 28.