[x+(y+1)][x-(y+1)]求平方差公式计算过程
问题描述：
[x+(y+1)][x-(y+1)]求平方差公式计算过程
答
[x+(y+1)][x-(y+1)]
=x²-(y+1)²
=x²-y²-2y-1(a+b+c)(a-b-c)也是一样(a+b+c)(a-b-c)=[a+(b+c)][a-(b+c)]=a²-(b+c)²=a²-b²-c²-2bc