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

﹙x-y﹚﹙x+y+x-y-2y﹚=2﹙x-y﹚﹙x-y﹚=2×3×3=18