Answer:
(3x +1)(x -7)
Step-by-step explanation:
Identify the first and last coefficients, and form their product.
(3)(-7) = -21
Find factor pairs of this number that have a sum equal to the middle coefficient.
-21 = (1)(-21) = (3)(-7) . . . . . sums are -20, -4
Rewrite the middle term as the sum of these factors.
3x^2 +x -21x -7
Factor pairs of terms.
x(3x +1) -7(3x +1) = (x -7)(3x +1) . . . . your factorization
