a> phan tich thanh nhan tu ; (x+1)(3X+2)=0
=> x=-1,2|3
c) f(x) = x^3 - 3x - 2
f(-1) = (-1)^3 -3(-1) - 2 = -1 + 3 - 2 = 0
x^3 - 3x - 2
= (x+1)(x^2 - x - 2)
= (x+1)(x^2 - 2x + x - 2)
= (x+1)(x(x-2)+1(x-2))
= (x+1)(x+1)(x-2)
= (x-2)(x+1)^2
x = {-1, -1, 2} x=-1