若a2=3a-1，则分式2a5-5a4+2a3-8a 2a2+1的值是_．
问题描述：
若a2=3a-1，则分式
的值是______． 2a5-5a4+2a3-8a 2
a2+1
答
原式=
2a3(a2+1)-a2(5a2+8)
a2+1
=
2a3(3a-1 +1)-a2[5(3a-1)+8]
a2+1
=
2a3•3a-a2[15a+3]
a2+1
=
6(3a-1)2-(3a-1)[15a+3]
a2+1
=
(3a-1)[6(3a-1)-(15a+3)]
a2+1
=
(3a-1)(3a-9)
a2+1
=
9(3a-1)-30a+9 3a
=
-3a 3a
=-1．
故答案为：-1．