tolong jawabannya terima kasih

x - 2 = 0
x = 2
f(2) = 0
(2)³ + a(2)² - 13(2) + b = 0
8 + 4a - 26 + b = 0
4a + b - 18 = 0
4a + b = 18
x - 1 = 0
x = 1
f(1) = 0
1³ + a(1)² - 13(1) + b = 0
1 + a - 13 + b = 0
a + b - 12 = 0
a + b = 12
eliminasi
4a + b = 18
a + b = 12
----------------_
3a = 6
a = 2
a + b = 12
2 + b = 12
b = 10
sudah ada dua faktor yaitu :
x = 2
dan
x = 1
jika ketiga nya dikalikan dihasilkan b
x × x × x = 10
2 × 1 × x = 10
x = 10/2 = 5
maka
x1 = 5
x2 = 2
x1 = 1
5 - 2 - 1 = 2
pilihan D