1/2X1/3-1/3X1/4-1/4X1/5-1/5X1/6.-1/39X1/40

来源:学生作业学帮网 编辑:学帮网 时间:2024/06/01 11:43:06

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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