（x+2y-3y)- (-2x-y+xy ) 其中x+y=0.5 xy等于-0.5_数学解答

（x+2y-3y)- (-2x-y+xy ) 其中x+y=0.5 xy等于-0.5

人气：250 ℃　时间：2020-02-05 21:21:59

解答

（x+2y-xy)- (-2x-y+xy )
=x+2y-xy+2x+y-xy
=3x+3y-2xy
=3(x+y)-2xy
=3×0.5-2×(-0.5)
=1.5+1
=2.5