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