Jika (x^2 - 4) adalah faktor dari x^3 - x^2 - ax + b maka nilai (a + b)(a - b) =

Bab Polinomial
Matematika SMA Kelas XI

x² - 4 = (x + 2) (x - 2)

x^3 - x² + ax + b = 0

2^3 - 2² - 2a + b = 0
-2a + b = - 4

(-2)^3 - (-2)² - (-2)a + b = 0
2a + b = 12

-2a + b = -4
2a + b = 12
----------------- +
2b = 8
b = 4

2a + b = 12
2a + 4 = 12
2a = 12 - 4
a = 8 : 2
a = 4

(a + b) (a - b)
= (4 + 4) (4 - 4)
= 0