由已知x+y=-2,xy=3那么2(x+xy)-[(xy-3y)-x]-(-xy)等于多少?

分类: 作业答案 • 2021-12-18 16:55:05

问题描述：

答

原式=2x+2xy-xy+3y+x+xy
=3x+3y+2xy
=3(x+y)+2xy
=-6+6
=0

答

2(x+xy)-[(xy-3y)-x]-(-xy)
=2x+2xy-xy+3y+x+xy
=2xy+3(x+y)
∵x+y=-2,xy=3
∴原式=6-6=0

答

2(x+xy)-[(xy-3y)-x]-(-xy)
=2x+2xy-xy+3y+x+xy
=3x+3y+2xy
=3（x+y）+2xy
=3*（-2）+2*3
=0