整体去括号；化简[5(x-y)-3(x-y)-(x-y)+2(x-y)]-2(x-y)
问题描述：
整体去括号；化简[5(x-y)-3(x-y)-(x-y)+2(x-y)]-2(x-y)
答
[5(x-y)-3(x-y)-(x-y)+2(x-y)]-2(x-y)
=（5-3-1+2）（x-y）-2（x-y)=（3-2）（x-y)=x-y中间是什么？不懂