清风蔓草
幼苗
共回答了8个问题 举报
1又1/15+3又1/35+5又1/63+7又1/99+9又1/143+11又1/195
=1+1/15+3+1/35+5+1/63+7+1/99+9+1/143+11+1/195
=1+3+5+7+9+11+1/15+1/35+1/63+1/99+1/143+1/195
=36+1/3*1/5+1/5*1/7+1/7*1/9+1/9*1/11+1/11*1/13+1/13*1/15
=36+1/2*(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13+1/13-1/15)
=36+1/2*(1/3-1/15)
=36又2/15
1年前
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