3a^2+ab-2b^2=0
(a+b)(3a-2b)=0
a+b=0或3a-2b=0
a=-b或a=2/3b
a/b-b/a-(a^2+b^2)/ab
=(a^2-b^2)/ab-(a^2+b^2)/ab
=-2b^2/(ab)
=-2b/a
=-2b/(-b)=2
或
=-2b/(2/3b)
=-3