1/a(a+1)+(a+1)(a+2)+1/(a+2)(a+3)+····1/(a+2009)(a+2010)

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1/a(a+1)+(a+1)(a+2)+1/(a+2)(a+3)+····1/(a+2009)(a+2010)
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1/a(a+1)+(a+1)(a+2)+1/(a+2)(a+3)+····1/(a+2009)(a+2010)
1/a(a+1)+(a+1)(a+2)+1/(a+2)(a+3)+····1/(a+2009)(a+2010)

1/a(a+1)+(a+1)(a+2)+1/(a+2)(a+3)+····1/(a+2009)(a+2010)
原式可转化为1/a-1/(a+1)+1/(a+1)-1/(a+2).-1/(1+2010)=1/a-1/(1+2010)

裂项求解
就是a分之一减(a+1)分之一……
就会得到
a分之一减(a+2010)分之一了

做差
2010/(2010 a + a^2)
楼上好快的身手————@@

1/a(a+1)
=[(a+1)-a]/a(a+1)
=(a+1)/a(a+1)-a/a(a+1)
=1/a-1/(a+1)
其他的以此类推
原式=[1/a-1/(a+1)]+[1/(a+1)-1/(a+2)]+……+[1/(a+2009)-1/(a+2010)]
中间正负抵消
=1/a-1/(a+2010)
=2010/a(a+2010)