Check my answer!

Factor completely: 6x2 - 12x - 18.

A. 3 (2x + 3) (x - 1)

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

C. 6 (x + 1) (x - 3)

D. 6 (x - 1) (x - 3)

The answer would have to be C. or D.

Factor out a 6

6 / 6x^2 = x^2

6 / - 12x = - 2x

6 / - 18 = - 3

6 (x^2 - 2x - 3)

Multiply the first term to the last

1 x - 3 = - 3

(a x b) = - 3

(a + b) = - 2 (middle term)

(1 x - 3) = - 3

(1 + - 3) = - 2

Plug them in by replacing - 2x and simplify

6 (x^2 - 1x - 3x - 3)

6 ((x^2 - 1x) - (3x - 3))

6 (x (x - 1) - 3 (x - 1))

6 (x - 3) (x - 1)

Or in this case, 6 (x - 1) (x - 3)