现规定│a b c d│=a-b+c-d,试化简.│xy-3x -2xy-x -2x-3 -5+xy│
问题描述：
现规定│a b c d│=a-b+c-d,试化简.│xy-3x -2xy-x -2x-3 -5+xy│
答
│xy-3x -2xy-x -2x-3 -5+xy│
=(xy-3x)-(-2xy-x)+(-2x-3)-(-5+xy)
=xy-3x+2xy+x-2x-3+5-xy
=-4x+2xy+2