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)