1/(2X3)+1/(3X4)+1/(4X5)+1/(5X6)+...+1/(100X101)=?
问题描述：
1/(2X3)+1/(3X4)+1/(4X5)+1/(5X6)+...+1/(100X101)=?
答
(1/2)-(1/3)........(1/100)-(1/101)=99/202
答
=(1/2-1/3)+(1/3-1/4)+……+(1/100-1/101)
中间正负抵消
=1/2-1/101
=99/202