(a2-a)a2-2a-3÷a(a-3)=a(a-1)(a+1)(a

(a2-a)
a2-2a-3÷
a
(a-3)
=
a(a-1)
(a+1)(a-3)×
a-3
a
=
a-1
a+1
当a=
2+1时，
原式=

2

2+1+1=

2

2+2=
2-1．
故填空答案：
2-1．