小学奥数题:3×5分之1+5×7分之1+................97×99分之1怎么算
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解决时间 2021-02-25 14:38
- 提问者网友:泪痣哥哥
- 2021-02-25 08:37
小学奥数题:3×5分之1+5×7分之1+................97×99分之1怎么算
最佳答案
- 五星知识达人网友:撞了怀
- 2021-02-25 09:25
3×5分之1=1/2*(1/3-1/5)
以此类推
原式=1/2*(1/3-1/5+1/5-1/7+1/7-1/9。。。。+1/97-1/99)
=1/2(1/3-1/99)
=16/99
以此类推
原式=1/2*(1/3-1/5+1/5-1/7+1/7-1/9。。。。+1/97-1/99)
=1/2(1/3-1/99)
=16/99
全部回答
- 1楼网友:胯下狙击手
- 2021-02-25 14:00
∵1/(3×5)=1/2*(1/3-1/5)
∴1/(3×5)+1/(5×7)+1/(7×9)+ --- +1/(97×99)
=1/2×(1/3-1/5+1/5-1/7+1/7-1/9+ --- +1/97-1/99)
=1/2×(1/3-1/99)
=16/99
∴1/(3×5)+1/(5×7)+1/(7×9)+ --- +1/(97×99)
=1/2×(1/3-1/5+1/5-1/7+1/7-1/9+ --- +1/97-1/99)
=1/2×(1/3-1/99)
=16/99
- 2楼网友:底特律间谍
- 2021-02-25 12:26
16/99
- 3楼网友:归鹤鸣
- 2021-02-25 11:49
=(3/1-1/5)/2+(5/1-7/1)/2+……
=(1/3-1/5+1/5-1/7……)/2
=(1/3-1/99)/2
=32/99/2
=16/99
对了吗?
=(1/3-1/5+1/5-1/7……)/2
=(1/3-1/99)/2
=32/99/2
=16/99
对了吗?
- 4楼网友:酒醒三更
- 2021-02-25 10:24
1/(3×5)+1/(5×7)+1/(7×9)+ --- +1/(97×99)
=1/2×(1/3-1/5+1/5-1/7+1/7-1/9+ --- +1/97-1/99)
=1/2×(1/3-1/99)
=16/99
=1/2×(1/3-1/5+1/5-1/7+1/7-1/9+ --- +1/97-1/99)
=1/2×(1/3-1/99)
=16/99
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