把(x+y),(x-y)个作为一个整体合并同类项

问题描述:

把(x+y),(x-y)个作为一个整体合并同类项
1,7(x+y)-2(x+y)-4(x+y)+2(x+y)
2,(x-y)²+2(x-y)-(x-y)-2(x-y)²

1,7(x+y)-2(x+y)-4(x+y)+2(x+y)
=3(x+y)
2,(x-y)²+2(x-y)-(x-y)-2(x-y)²
=-(x-y)²+(x-y)