x(y-3)-(2y-6)=x(y-3)-2(y-3)=(y-3)(y-2)(x+y)^3-(x-y)^2(x+y)=(x+y)[(x+y)^2-(x-y)^2]=(x+y)[(x+y+x-y)(x+y-x+y)]=(x+y)*2x*2y=4xy(x+y)x(x^2-xy)-(4x^2-4xy)=x^2(x-y)-4x(x-y)=x(x-y)(x-4)
