x^3y-2x^2*y^2+xy^3=xy(x^2-2xy+y^2)=xy(x-y)^2=2*1^2=2
x^3y-2x^2*y^2+xy^3=x^2y(x-y)+xy^2(y-x)=x^2y-xy^2=xy(x-y)=2
