factor the following... x^2+8x+12

list the factors of 12,

2 * 6
3 * 4
12 * 1

Now, when added, must equal 8
2 * 6 = 8
3 * 4 = 7
12 * 1 = 12

so, since 2 * 6 = 12 and 2 + 6 = 8
x^2+8x+12
(x + 2)(x + 6)