计算:1/(1×2)+1/(2×3)+1/(3×4)+.+1/(2009×1010)

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计算:1/(1×2)+1/(2×3)+1/(3×4)+.+1/(2009×1010)
计算:1/(1×2)+1/(2×3)+1/(3×4)+.+1/(2009×1010)

计算:1/(1×2)+1/(2×3)+1/(3×4)+.+1/(2009×1010)
=1-1/2+1/2-1/3+1/3-1/4+.+1/2009-1/2010
=1-1/2010
=2009/2010

1/(1*2)=1/2
1/(1*2)+1/(2*3)=2/3
1/(1*2)+1/(2*3)+1/(3*4)=3/4
所以
1/1*2+1/2*3+1/3*4+1/4*5......1/2009*2010=2009/2010

原式=1-1/2+1/2-1/3+1/3-1/4+1/4.....-1/2010
=1-1/2010
=2009/2010

裂项法:第一项=1-1/2;第二项=1/2-1/3.......结果前后相邻两项抵消了,只剩下1-1/2010。