根据数列极限的夹逼性
因为n[1/(n^2+1)+1/(n^2+2)+...+1/2n^2]
n[1/2n^2+1/2n^2+...+1/2n^2]
=n^3/2n^2
=n/2
因为n^3/(n^2+1)和n/2都趋向于+∞
所以原式也趋向于+∞