(x+y)(x+y)(x+y)(x+y)(x+y)(x+y)
(x+y)(x−y)(x+y)(x-y)(x+y)(x−y)
(x−y)(x−y)(x-y)(x-y)(x−y)(x−y)
(y+x)(y−x)(y+x)(y-x)(y+x)(y−x)