6x^3-5x^2y-3xy^2+2y^3
=6x^2*(x-y)+x^2y-xy^2-2y^2(x-y)
=6x^2*(x-y)+xy(x-y)-2y^2(x-y)
=(x-y)(6x^2+xy-2y^2)
=(x-y)(2x-y)(3x+2y)