y=(x^2+x-1)/(x^2+x-6)
=(x^2+x-1-5+5)/(x^2+x-6)
=1+5/(x^2+x-6)
函数 f(x)=x^2+x-6有最小值,故原式有最大值
x=-b/2a=-1/2
即x=-1/2时有最大值,代入可得
1+5/(1/4-1/2-6)
=1-5*4/25
=1/5