由题设0＜x＜y

∵xy=9，∴

xy

=3

∴x+y-2

xy

=(x

1

2

-y

1

2

)2=12-6=6

x+y+2

xy

=(x

1

2

+y

1

2

)2=12+6=18

∴x

1

2

-y

1

2

=-

6

，x

1

2

+y

1

2

=3

2

∴

x 1 2 -y 1 2

x 1 2 +y 1 2

=

- 6

3 2

=-

3

3

故答案为：-

3

3