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(1减1/2)加(1/2减1/3)加(1/3减1/4)加(1/4减1/5).(1/2010减1/2011)=1 - 1/2011(注:中間相鄰兩項互相抵消,比如- 1/2與1/2的和等於0,依次類推)=2000/2011
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