求"4-2分之1-6分之5-12分之11-20分之19"的简便运算
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![求](/uploads/image/z/111689-17-9.jpg?t=%E6%B1%82%224-2%E5%88%86%E4%B9%8B1-6%E5%88%86%E4%B9%8B5-12%E5%88%86%E4%B9%8B11-20%E5%88%86%E4%B9%8B19%22%E7%9A%84%E7%AE%80%E4%BE%BF%E8%BF%90%E7%AE%97)
求"4-2分之1-6分之5-12分之11-20分之19"的简便运算
求"4-2分之1-6分之5-12分之11-20分之19"的简便运算
求"4-2分之1-6分之5-12分之11-20分之19"的简便运算
4-2分之1-6分之5-12分之11-20分之19"的简便运算
解,得:
4-(1/2)-(5/6)-(11/12)-(19/20)
==4-[1-(1/2)]-[1-(1/6)]-[1-(1/12)]-[1-(1/20)]
==4-1-1-1-1+(1/2)+(1/6)+(1/12)+(1/20)
==1/2+1/6+1/12+1/20
==1-1/2+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)
===1-1/2+1/2-1/3+1/3-1/4+1/4-1/5
==1-1/5
==4/5
标准答案:
4-1/2-5/6-11/12-19/20
=4-(1-1/2)-(1-1/6)-(1-1/12)-(1-1/20)
=4-1+1/2-1+1/6-1+1/12-1+1/20
=1/2+1/6+1/12+1/20
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5
=1-1/5
=4/5
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4-1/2-5/6-11/12-19/20
=4-(1-1/2)-(1-1/6)-(1-1/12)-(1-1/20)
=4-1+1/2-1+1/6-1+1/12-1+1/20
=1/2+1/6+1/12+1/20
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5
=1-1/5
=4/5
4-1/2-5/6-11/12-19/20=(1-1/2)+(1-5/6)+(1-11/12)+(1-19/20)
=1/2-1/6-1/12-1/20
=1/2-(1/2-1/3)-(1/3-1/4)-(1/4-1/5)
=1/2-1/2+1/3-...
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4-1/2-5/6-11/12-19/20=(1-1/2)+(1-5/6)+(1-11/12)+(1-19/20)
=1/2-1/6-1/12-1/20
=1/2-(1/2-1/3)-(1/3-1/4)-(1/4-1/5)
=1/2-1/2+1/3-1/3+1/4-1/4+1/5
=1/5
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