已知x-y=3,求代数式（x+y)(x-y)+(x-y)²-（2xy-2y)²的值
问题描述：
已知x-y=3,求代数式（x+y)(x-y)+(x-y)²-（2xy-2y)²的值
答
（x+y)(x-y)+(x-y)²-（2xy-2y)²
=（x+y)(x-y)+(x-y)²-4y^2（x-1)²
=-4y^2（x-1)²
答
（x+y)(x-y)+(x-y)²-（2xy-2y)²
=（x+y)(x-y)+(x-y)²-4y^2（x-1)²
=-4y^2（x-1)²
只能到这了啊
答
﹙x－y﹚﹙x＋y＋x－y－2y﹚=2﹙x－y﹚﹙x－y﹚=2×3×3=18