1/n(n+1)=1/n-1/(n+1)
1/(1*2) +1/(2*3)+…… 1/n(n+1)=1-1/2+1/2-1/3+……+1/n-1/(n+1)
=1-1/(n+1)
lim { 1/(1*2) +1/(2*3)+…… 1/n(n+1)}n箭头无限=1
1/n(n+1)=1/n-1/(n+1)
1/(1*2) +1/(2*3)+…… 1/n(n+1)=1-1/2+1/2-1/3+……+1/n-1/(n+1)
=1-1/(n+1)
lim { 1/(1*2) +1/(2*3)+…… 1/n(n+1)}n箭头无限=1