原式=1/2(1/1*2-1/2*3)+1/2(1/2*3-1/3*4)+1/2(1/3*4-1/4*5)+.+1/2(1/98*99-1/99*100)
=1/2(1/1*2-1/2*3+1/2*3-1/3*4+1/3*4-1/4*5+.+1/98*99-1/99*100)
=1/2(1/1*2-1/99*100)
=4949/19800
1/1*2*3+1/2*3*4+1/3*4*5+.+1/98*99*100 等于几?
1/1*2*3+1/2*3*4+1/3*4*5+.+1/98*99*100 等于几?
数学人气:893 ℃时间:2020-02-03 01:44:17
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