12xy(m-n)-x^2*(n-m)^2 =12xy(m-n)-x^2*(m-n)^2 =x(m-n)[12y-x*(m-n)] =x(m-n)(12y-mx+nx) x(x-2y)(a-b)-y(2y-x)(b-a) =x(x-2y)(a-b)-y[-(x-2y)*-(a-b)] =x(x-2y)(a-b)-y(x-2y)(a-b) =(x-y)(x-2y)(a-b)