（
1
a 2 -a+1 -
1-a
a 3 -1 ）÷
a 4 - a 2 -2
( a 6 -1)-( a 4 + a 2 +1)
=（
1
a 2 -a+1 +
a-1
(a-1)( a 2 +a+1) ）÷
( a 2 -2)( a 2 +1)
( a 4 + a 2 +1)( a 2 -1-1)
=
a 2 +a+1+ a 2 -a+1
( a 2 -a+1)( a 2 +a+1) •
a 4 + a 2 +1
a 2 +1
=
2( a 2 +1)
a 2 +1 =2．
故答案为：2．