1/1X2+1/2X3+1/3X4+...+1/n(n+1)等于几?
问题描述：
1/1X2+1/2X3+1/3X4+...+1/n(n+1)等于几?
答
=1-1/2+1/2-1/3+1/3-1/4……+1/n-1/(n+1)=1-1/(n+1)=n/(n+1)
1/1X2+1/2X3+1/3X4+...+1/n(n+1)等于几?
=1-1/2+1/2-1/3+1/3-1/4……+1/n-1/(n+1)=1-1/(n+1)=n/(n+1)