1/(13×15)+1/(15×17)+1/(17×19)+…1/(37×39)=
问题描述：
1/(13×15)+1/(15×17)+1/(17×19)+…1/(37×39)=
答
1/（13*15）=[1/13-1/15]/2
1/（15*17）=[1/15-1/17]/2
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1/(13×15)+1/(15×17)+1/(17×19)+…1/(37×39)=[1/13-1/39]/2
=1/39