caculation:2/(1+2) + (2+3)/(1+2+3) +(2+3+4)/(1+2+3+4) + .+ (2+3+4+...+2009)/(1+2+3+4+...+2009)

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caculation:2/(1+2)+(2+3)/(1+2+3)+(2+3+4)/(1+2+3+4)+.+(2+3+4+...+2009)/(1+2+3+4+...+2009)caculation:2

caculation:2/(1+2) + (2+3)/(1+2+3) +(2+3+4)/(1+2+3+4) + .+ (2+3+4+...+2009)/(1+2+3+4+...+2009)
caculation:
2/(1+2) + (2+3)/(1+2+3) +(2+3+4)/(1+2+3+4) + .+ (2+3+4+...+2009)/(1+2+3+4+...+2009)

caculation:2/(1+2) + (2+3)/(1+2+3) +(2+3+4)/(1+2+3+4) + .+ (2+3+4+...+2009)/(1+2+3+4+...+2009)
1-1/(1+2)+1-1/(1+2+3)+1-1/(1+2+3+4)+……+1-1/(1+2+3+4+...+2009)
=2008-【1/(1+2)+1/(1+2+3)+1/(1+2+3+4)+……+1/(1+2+3+4+...+2009)】
=2008-2×【（1/6+1/12+1/24+……+1/（2009×2010）】
=2008-2×（1/2-1/2010）
=2007+1/1005

2/(1+2) + (2+3)/(1+2+3) +(2+3+4)/(1+2+3+4) + ....+ (2+3+4+...+2009)/(1+2+3+4+...+2009)
=2008-[1/(1+2) + 1/(1+2+3) +1/(1+2+3+4) + ....+ 1/(1+2+3+4+...+2009)]
=2008-(2/2*3+2/3*4+2/4*5+……+2/2009*...

全部展开

2/(1+2) + (2+3)/(1+2+3) +(2+3+4)/(1+2+3+4) + ....+ (2+3+4+...+2009)/(1+2+3+4+...+2009)
=2008-[1/(1+2) + 1/(1+2+3) +1/(1+2+3+4) + ....+ 1/(1+2+3+4+...+2009)]
=2008-(2/2*3+2/3*4+2/4*5+……+2/2009*2010）
=2008-2*（1/2-1/3+1/3-1/4+1/4-1/5+……+1/2009-1/2010）
=2008-2*（1/2-1/2010）
=2008-（1-1/1005）
=2007又1/1005

收起

通项公式为：(n(n+1)-2)/(n(n+1))=1-2/(n(n+1))=1-2(1/n-1/(n+1))
所以原式=
1x2008 - 2x（1/2 - 1/3 + 1/3 -1/4 +。。。+1/2009 -1/2010）
=2008-2x（1/2-1/2010）
=2008-1+1/1005
=2007又1/1005

会不会：(2+3+...+n)/(1+2+3+...+n)=[(n+2)(n-1)/2]/[(n+1)n/2]=1-2/[n(n+1)]=1-2[1/n-1/(n+1)]

2/(1+2) + (2+3)/(1+2+3) +(2+3+4)/(1+2+3+4) + ....+ (2+3+4+...+2009)/(1+2+3+4+...+2009)
=1-2(1/2-1/3)...

全部展开

会不会：(2+3+...+n)/(1+2+3+...+n)=[(n+2)(n-1)/2]/[(n+1)n/2]=1-2/[n(n+1)]=1-2[1/n-1/(n+1)]

2/(1+2) + (2+3)/(1+2+3) +(2+3+4)/(1+2+3+4) + ....+ (2+3+4+...+2009)/(1+2+3+4+...+2009)
=1-2(1/2-1/3)+1-2(1/3-1/4)+1-2(1/4-1/5)+...+1-2(1/2009-1/2010)
=2009-1-2(1/2-1/3+1/3-1/4+1/4-1/5+...+1/2009-1/2010)
=2008-2(1/2-1/2010)
=2008-1+1/1005
=2007又1/1005

收起

caculation:2/(1+2) + (2+3)/(1+2+3) +(2+3+4)/(1+2+3+4) + .+ (2+3+4+...+2009)/(1+2+3+4+...+2009) 英译汉一段话The horizontal axis considers processes,reflecting how far strategies are the product of deliberae caculation or whether they emerge by accident,muddle or intertia... 帮忙几道改错题1.For you are free tonight ,why not drop in and play chess with me2.If only the caculation is right,scientist can never be sure that thay have included all variables and modeled them accurately.3.however difficult is english ,i w how could you make sure of 9% by the trial and error method?hi,there!i do not know who you are,buddy.however,i read you article over this webpage,regarding to caculation of real interest rate,where i found that you illustrated the method of trial and 1 2 1 2 () () ()() 1+1/2^2 (2-×)(1-×)=×-2-2(2-×)(1-×) 1+2+1+2+1+2+1+2+1+2+1+2+1+2 =( )*( ) =() 比如2^1、2^2? 1/2+1/2*2+1/2*2*2+1/2*2*2*2+.+1/2*n 2 1 -2 -3 2”表示“【1,2)” 谁能解便计算这道题1+2+2+2+1+2+2+2+2+2+1+1 1/2^-2=? 2i/2-1 loga(1/2)>2 (x+1/2)2 1,2,