1/n^2+2/n^2+3/n^2...+n/n^2)=n(n+1)/2n^2=1/2+1/n^2
n→+∞ lim(1/n2+2/n2+3/n2...+n/n2)=1/2+lim1/n^2
=1/2+0 =1/2