1/(1+2)+1/(1+2+3)+.+1/(1+2+3+.+100)
=2/(2*3)+2/(3*4)+.+2/(100*101)
=2(1/2-1/3+1/3-1/4+1/4-1/5+.+1/100-1/101)
=2*(1/2-1/101)
=99/101
1/(1+2)+1/(1+2+3)+.+1/(1+2+3+.+100)=?
1/(1+2)+1/(1+2+3)+.+1/(1+2+3+.+100)=?
数学人气:123 ℃时间:2020-06-21 02:03:25
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