x的立方-6x的平方+11x-6
=x^3-6x^2+9x+2x-6
=(x^3-6x+9x)+(2x-6)
=x(x^2-6x+9)+2(x-3)
=x(x-3)^2+2(x-3)
=(x-3)(x^2-3x+2)
=(x-3)(x-1)(x-2)