a²-ab-2b²=(a-2b)(a+b)=0
a=2b或a=-b
a=2b
则a/b-b/a-(a²+b²)/ab
=2b/b-b/2b-(4b²+b²)/(2b²)
=2-1/2-5/2
=-1
a=-b
则a/b-b/a-(a²+b²)/ab
=-b/b-b/(-b)-(b²+b²)/(-b²)
=-1+1+2
=2
所以原式=-1或2