2/1*4+2/4*7+2/7*10+2/10*13...+2/97*100

发布时间：2020-07-28 21:48:59

如上

网友回答

=2*[1/(1*4)+1/(4*7)+1/(7*10)+....+1/(97*100)]
=2*[1/3*(1-1/4)+1/3*(1/4-1/7)+1/3*(1/7-1/10)+....+1/3*(1/97-1/100)]
=2*[1/3*(1-1/4+1/4-1/7+1/7-1/10+......+1/97-1/100)]
=2*[1/3*(1-1/100)]
=33/50
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