- 2(x-y)^2- 3(x-y)+5(y-x)^2+4(y-x)
=-(x-y)(2x-2y+3)+(y-x)(5y-5x+4)
=(y-x)(2x-2y+3)+(y-x)(5y-5x+4)
=(y-x)(2x-2y+3+5y-5x+4)
=(y-x)(3y-3x+7)