x趋于1时,limf(x)=(x^3-kx+1)/(x^2-1)
要使极限存在,需分子趋于0.1-k+1=0,所以k=2
limf(x)=(x^3-2x+1)/(x^2-1)=lim(3x^2-2)/2x=1/2
l=1/2
(2,1/2)