f(x)=e^x/(1+ax^2) f'(x)=[e^x(1+ax^2)-2axe^x]/(1+ax^2)^2=e^x(ax^2-2ax+1)/(1+ax^2)^2=ae^x[(x-1)^2+1/a-1]/(1+ax^2)^2 讨论a: 若0x1,或x
