Factor the following:
2 x^3 + x^2 - 18 x - 9
Factor terms by grouping. 2 x^3 + x^2 - 18 x - 9 = (2 x^3 + x^2) + (-18 x - 9) = x^2 (2 x + 1) - 9 (2 x + 1):
x^2 (2 x + 1) - 9 (2 x + 1)
Factor 2 x + 1 from x^2 (2 x + 1) - 9 (2 x + 1):
(2 x + 1) (x^2 - 9)
x^2 - 9 = x^2 - 3^2:
(2 x + 1) (x^2 - 3^2)
Factor the difference of two squares. x^2 - 3^2 = (x - 3) (x + 3):
Answer: (x - 3) (x + 3) (2 x + 1) thus the Answer is C.
