把x-y看成一个整体,合并同类项:5(x-y)+3(x-y)-7(x-y)

问题描述:

把x-y看成一个整体,合并同类项:5(x-y)+3(x-y)-7(x-y)

5(x-y)+3(x-y)-7(x-y)=(5+3-7)(x-y)=x-y可是我这样写老师打错