Hoặc
xx+y+2xyx2−y2−yx+y
=xx+y−yx+y+2xyx2−y2
=x−yx+y+2xyx+yx−y
=x−y2x+yx−y+2xyx+yx−y
=x2−2xy+y2+2xyx+yx−y
=x2+y2x+yx−y
