1/1x5+1/5x9+1/9x13……+1/101x105=1/4(1-1/5+1/5-1/9+1/9-1/13+……+1/101-1/105)=1/4(1-1/105)=1/4 x 104/105=26/105【1/n(n+m)=1/m x (1/n-1/(n+m))】希望能够帮到你,祝你学习愉快!