用裂项法:1/2=1/1*2=1-1/2,1/6=1/2*3=1/2-1/3,依次类推……所以原式=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+……+(1/2005-1/2006)=1-1/2006=2005/2006.
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用裂项法:1/2=1/1*2=1-1/2,1/6=1/2*3=1/2-1/3,依次类推……所以原式=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+……+(1/2005-1/2006)=1-1/2006=2005/2006.