问题
选择题
已知
|
答案
∵
-1 x
=1 y
=2,即y-x=2xy,y-x xy
∴x-y=-2xy,
则
=5x+xy-5y x-xy-y
=5(x-y)+xy (x-y)-xy
=-10xy+xy -2xy-xy
=3.-9xy -3xy
故选D
已知
|
∵
-1 x
=1 y
=2,即y-x=2xy,y-x xy
∴x-y=-2xy,
则
=5x+xy-5y x-xy-y
=5(x-y)+xy (x-y)-xy
=-10xy+xy -2xy-xy
=3.-9xy -3xy
故选D