Factor x^3 +2x^2 -9x -18, given that -2 is a zero

Step-by-step explanation:

Take out the common factor from the first and second terms and again from the 3rd and fourth terms.

x^2(x + 2) - 9(x + 2)

Take out x + 2 from around the minus sign.

(x + 2)(x^2 - 9)

Factor x^2 - 9 which will come out to the difference of squares.

(x + 2)(x + 3)(x - 3)

This is how it factors.

You could also use synthetic division if you know how it works.

-2 || 1    2   -9     -18

          -2    0      18

      1    0    -9      0

This gives you (x + 2)(x^3 - 9) just as before.