SAT Equivalent expressions Practice Question 12 (Medium)

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Math · Advanced MathMedium

Which expression is equivalent to $9x^2 - 30x + 25$ ?

$(3x + 5)^2$

$(9x - 5)(x - 5)$

$(3x - 5)(3x + 5)$

$(3x - 5)^2$

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Answer: D

The first and last terms are perfect squares: $9x^2 = (3x)^2$ and $25 = 5^2$ . The middle term is $-2(3x)(5) = -30x$ , so the expression is $(3x - 5)^2$ .

Choice A has the right squares but gives a middle term of $+30x$ .

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