Question

what is the completely factored form of this expression?
$3x^2 - 17x - 28$
a. $(3x + 4)(x + 7)$
b. $(3x + 4)(x - 7)$
c. $3x^2 - 17x - 28$
d. $(3x^2 + 4)(x - 7)$

Explanation:

Step1: Expand option A

$(3x+4)(x+7)=3x^2+21x+4x+28=3x^2+25x+28$ (not match)

Step2: Expand option B

$(3x+4)(x-7)=3x^2-21x+4x-28=3x^2-17x-28$ (matches)

Step3: Check other options

Option C is original (not factored); Option D expands to $3x^3-21x^2+4x-28$ (not match)

Answer:

B. (3x + 4)(x - 7)