Question

若

1

x

-

1

y

=3，求

2x+3xy-2y

x+2xy-y

的值=______．

Answer 1

∵

1

x

-

1

y

=3，∴x-y=-3xy，再把它整体代入原式：

2x+3xy-2y

x+2xy-y

=

2(x-y)+3xy

(x-y)+2xy

=

-6xy+3xy

-3xy+2xy

=

-3xy

-xy

=3．
故答案为3．