n趋向什么呢?假设是无限吧lim[n→∞] (n+1)/(n+2)=lim[n→∞] (1+1/n)/(1+2/n)=(1+0)/(1+0)=1lim[n→∞] (n²-1)/(2n²+1)=lim[n→∞] (1-1/n²)/(2+1/n²)=(1-0)/(2+0)=1/2