把(x-y)看作一个整体,合并同类项:5(x-y)+2(x-y)-4(x-y)=_.

问题描述:

把(x-y)看作一个整体,合并同类项:5(x-y)+2(x-y)-4(x-y)=______.

5(x-y)+2(x-y)-4(x-y)=(5+2-4)(x-y)=3(x-y).