lim[x^2/(x+1)-ax-b]=0
===> lim[x^2/(x+1)-(ax+b)]=0
===> lim[x^2-(x+1)(ax+b)]/(x+1)=0
===> lim[(1-a)x^2-(a+b)x-b]/(x+1)=0
===> 1-a=0,且a+b=0
所以,a=1,b=-1
lim[x^2/(x+1)-ax-b]=0
===> lim[x^2/(x+1)-(ax+b)]=0
===> lim[x^2-(x+1)(ax+b)]/(x+1)=0
===> lim[(1-a)x^2-(a+b)x-b]/(x+1)=0
===> 1-a=0,且a+b=0
所以,a=1,b=-1