解:本题典型的分类讨论题!1)当x=1时,e^[n(x-1)]=1于是,原函数f(x)=lim (a+b)/2 =(1+a+b)/22)当x<1时,0原函数f(x)=lim (ax+b)=ax+b3)当x>1时e^[n(x-1)] >1,lim 1/e^[n(x-1)] =0f(x)=lim {x²+{(ax+b)/e^[n(x-1)]}}/{1+{1/e^[n(x-1)]}} =x²综合:f(x)在R上连续,因此:(1+a+b)/2 = a+b = 1所以,a+b=1