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

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

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

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