Factor the quadratic 12 x^2 + 17 x + 6. The coefficient of x^2 is 12 and the constant term is 6. The product of 12 and 6 is 72. The factors of 72 which sum to 17 are 8 and 9. So 12 x^2 + 17 x + 6 = 12 x^2 + 9 x + 8 x + 6 = 3 (3 x + 2) + 4 x (3 x + 2):
