√(b^2-4ac)/(a的绝对值)=√91/6
(b^2-4ac)/a^2=91/36
36(b^2-4ac)=91a^2
2a+3b=-4c
36[b^2+a(2a+3b)]=91a^2
36b^2+72a^2+108ab=91a^2
19a^2-108ab-36b^2=0
a=(108b+120b)/38=228b/38=6b
x=-b/2a=-1/12
或a=(108b-120b)/38=-12b/38=-6b/19
x=-b/2a=19/12
出抛物线的对称轴方程为:x=-1/12或x=19/12