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

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

人气：414 ℃　时间：2019-10-05 13:59:16

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