persamaan nilai mutlak x2 - 4x -12 = 9

| x^2 - 4x - 12 | = 9 <=> x^2 - 4x - 12 = 9 atau x^2 - 4x - 12 = -9
selanjutnya, jika x^2 - 4x - 12 = 9, maka x^2 - 4x - 21 = 0 <=> (x - 7)(x + 3) = 0 <=> x = 7 atau x = -3
jika x^2 - 4x - 12 = -9, maka x^2 - 4x - 3 = 0 <=> x = 2 + akar7 atau x = 2 - akar7