作业帮1/2X1/3-1/3X1/4-1/4X1/5-1/5X1/6.-1/39X1/40
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/11 21:12:14
1/2X1/3-1/3X1/4-1/4X1/5-1/5X1/6.-1/39X1/40
1/2X1/3-1/3X1/4-1/4X1/5-1/5X1/6.-1/39X1/40
1/2X1/3-1/3X1/4-1/4X1/5-1/5X1/6.-1/39X1/40
1/2X1/3=1/2--1/3
1/3X1/4=1/3--1/4
.
依次类推最后结果=1/2--1/140=69/140
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