1/(1+2)=2*(1/2-1/3)
1/(1+2+3)=2*(1/3-1/4)
1/(1+2+3+4)=2*(1/4-1/5)
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1/(1+2+……+k)=2*【1/k-1/(1+k)】
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1/(1+2+3+...+99)=2*(1/99-1/100)
连加得1/(1+2)+1/(1+2+3)+1/(1+2+3+4)+.+1/(1+2+3+...+99)=2*(1/2-1/3+1/3-1/4+1/4-1/5+……+1/k-1/(1+k)+……+1/99-1/100)=2*(1/2-1/100)=49/50=0.98