如图
x^2+1=x(x+1) -x+1=x(x+1) -(x+1) +2lim(x->∞) [ (x^2+1)/(x+1) - ax -b)=0lim(x->∞) [ ( x-1) + 2/(x+1) - ax -b)=0lim(x->∞) [ (1-a)x+(-1-b) + 2/(x+1) ]=0=>1-a=0 and -1-b=0a=1 and b=-1
