1/2-1/n+1<1/2^2+1/3^2+……+1/n^2<n-1/n(n=2,3,4,5,6.

问题描述:

1/2-1/n+1<1/2^2+1/3^2+……+1/n^2<n-1/n(n=2,3,4,5,6.
1/2-1/(n+1)<1/(2^2)+1/(3^2)+……+1/(n^2)<(n-1)/n

证明:1/i-1/(i+1)=1/(i(i+1))