(x+2y-3xy+2x+y-xy)-(-2-y+xy),其中x+y=2分之1,xy=-2分之1_数学解答

(x+2y-3xy+2x+y-xy)-(-2-y+xy),其中x+y=2分之1,xy=-2分之1

人气：493 ℃　时间：2019-12-18 09:21:51

解答

（x+2y-3xy)-(-2x-y+xy)
=x+2y-3xy+2x+y-xy
=(1+2)x+(2+1)y-(3+1)xy
=3x+3y-4xy
=3(x+y)-4xy
=3*1/2-4*(-1/2)
=3/2+4/2
=7/2