(5x-3y)-[(5x-2xy-y)-(x-2xy+3y)];其中x=-2;y=-1/2

问题描述:

(5x-3y)-[(5x-2xy-y)-(x-2xy+3y)];其中x=-2;y=-1/2

=5x-3y-(5x-2xy-y-x+2xy-3y) =5x-3y-(4x-4y) =5x-3y-4x+4y =x+y 当x=-2,y=-1/2时 4+1/4=17/4