1/1×3+1/3×5+1/5×7+…1/17×19+1/19×21这道题如何简便运算?(步骤、解释、分析)=1/2*(2/(1*3)+2/(3*5)+2/(5*7)+...+2/(19*21)) =1/2*(1-1/3+1/3-1/5+1/5-1/7+...+1/19-1/21) =1/2*(1-1/21) =10/21 二分之一哪来的?为什么要一减
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![1/1×3+1/3×5+1/5×7+…1/17×19+1/19×21这道题如何简便运算?(步骤、解释、分析)=1/2*(2/(1*3)+2/(3*5)+2/(5*7)+...+2/(19*21)) =1/2*(1-1/3+1/3-1/5+1/5-1/7+...+1/19-1/21) =1/2*(1-1/21) =10/21 二分之一哪来的?为什么要一减](/uploads/image/z/118851-51-1.jpg?t=1%2F1%C3%973%2B1%2F3%C3%975%2B1%2F5%C3%977%2B%E2%80%A61%2F17%C3%9719%2B1%2F19%C3%9721%E8%BF%99%E9%81%93%E9%A2%98%E5%A6%82%E4%BD%95%E7%AE%80%E4%BE%BF%E8%BF%90%E7%AE%97%3F%EF%BC%88%E6%AD%A5%E9%AA%A4%E3%80%81%E8%A7%A3%E9%87%8A%E3%80%81%E5%88%86%E6%9E%90%EF%BC%89%3D1%2F2%2A%282%2F%281%2A3%29%2B2%2F%283%2A5%29%2B2%2F%285%2A7%29%2B...%2B2%2F%2819%2A21%29%29+%3D1%2F2%2A%281-1%2F3%2B1%2F3-1%2F5%2B1%2F5-1%2F7%2B...%2B1%2F19-1%2F21%29+%3D1%2F2%2A%281-1%2F21%29+%3D10%2F21+%E4%BA%8C%E5%88%86%E4%B9%8B%E4%B8%80%E5%93%AA%E6%9D%A5%E7%9A%84%3F%E4%B8%BA%E4%BB%80%E4%B9%88%E8%A6%81%E4%B8%80%E5%87%8F)
1/1×3+1/3×5+1/5×7+…1/17×19+1/19×21这道题如何简便运算?(步骤、解释、分析)=1/2*(2/(1*3)+2/(3*5)+2/(5*7)+...+2/(19*21)) =1/2*(1-1/3+1/3-1/5+1/5-1/7+...+1/19-1/21) =1/2*(1-1/21) =10/21 二分之一哪来的?为什么要一减
1/1×3+1/3×5+1/5×7+…1/17×19+1/19×21这道题如何简便运算?(步骤、解释、分析)
=1/2*(2/(1*3)+2/(3*5)+2/(5*7)+...+2/(19*21)) =1/2*(1-1/3+1/3-1/5+1/5-1/7+...+1/19-1/21) =1/2*(1-1/21) =10/21 二分之一哪来的?为什么要一减三分之一?我看不懂,帮我解释一下!
1/1×3+1/3×5+1/5×7+…1/17×19+1/19×21这道题如何简便运算?(步骤、解释、分析)=1/2*(2/(1*3)+2/(3*5)+2/(5*7)+...+2/(19*21)) =1/2*(1-1/3+1/3-1/5+1/5-1/7+...+1/19-1/21) =1/2*(1-1/21) =10/21 二分之一哪来的?为什么要一减
你不用看后面那么多,看前面几个 后面都是循环的,1/2*(2/(1*3)+2/(3*5))是不是等于1/1×3+1/3×5就相当于乘以2除以2(2/1×1*2)减1/3也是1-1/3=2/(1*3)把这个拆开了
每一项都乘以2和1/2,再把每一项的1/2都提出来。
2/(1*3)=2/3=1-1/3
1/1*3+1/3*5+1/5*7……+1/17*19
简算:1/(1*3)+1/(3*5)+1/(5*7)+……+1/(99*101)=
1/1*3+1/3*5+1/5*7……1/97*99=
1×3/1+3×5/1+5×7/1……+49×51/1
1/1×3 1/3×5 1/5×7 …… 1/2009×2010等于多少
1/1*3+1/3*5+1/5*7+……+1/2003*2005结果是什么?
1/1×3+1/3×5+1/5×7+……+1/47×49简便计算
1/1*3+1/3*5+1/5*7+……+1/47*49
1/3×1/5+1/5×1/7+1/7×1/9+……+1/97×1/99
1+1/1*3+1/3*5+1/5*7+1/7*9+……+1/99*101=?
1×1/3+1/3×1/5+1/5×1/7+……+1/99×1/101
1/3*5+1/5*7+1/7*9+……1/97*99
计算1/1×3+1/3×5+1/5×7+…+1/1997×1999
计算:1/1*3+1/3*5+1/5*7+…+1/99*101.怎么来?
1/(1+3)+1/(3+5)+1/(5+7)…+1/(99+101)=( )简便计算
1/1*3+1/3*5+1/5*7+…+1/97*99找规律计算
1/1×3+1/3×5+1/5×7+…+1/99×101 等于多少啊
1/3×1+1/3×5+1/5×7…1/2009×2011等于多少