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1-5/6+7/12-9/20-11/30-13/42+15/56-17/72+19/90

来源:学生作业帮 编辑:百度作业网作业帮 分类:数学作业 时间:2024/04/30 06:16:01
1-5/6+7/12-9/20-11/30-13/42+15/56-17/72+19/90
1又1/2-6/7+7/12-9/20+11/30-13/42
要简便,有规律!
1-5/6+7/12-9/20-11/30-13/42+15/56-17/72+19/90
应该是1-5/6+7/12-9/20+11/30-13/42+15/56-17/72+19/90=

1-5/6+7/12-9/20+11/30-13/42+15/56-17/72+19/90
=1-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)+(1/7+1/8)-(1/8+1/9)+(1/9+1/10)
=1-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7+1/7+1/8-1/8-1/9+1/9+1/10
=1-1/2+1/10
=3/5
若你的正确:则
1-1/6+7/12-9/20+11/30-13/42+15/56-17/72+19/90=
=1-(1/2-1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)+(1/7+1/8)-(1/8+1/9)+(1/9+1/10)
=1-1/2+1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7+1/7+1/8-1/8-1/9+1/9+1/10
=1-1/2+2/3+1/10
=19/15