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colon20001 幼苗
共回答了26个问题 举报
1/3+1/15+1/35+1/63+1/99
=(1/2)*(1/1-1/3)+(1/2)*(1/3-1/5)+(1/2)*(1/5-1/7)
+(1/2)*(1/7-1/9)+(1/2)*(1/9-1/11)
=(1/2)*(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)
=(1/2)*(1/1-1/11)
=5/11
=(1/2)*(1/1-1/3)+(1/2)*(1/3-1/5)+(1/2)*(1/5-1/7)
+(1/2)*(1/7-1/9)+(1/2)*(1/9-1/11)
=(1/2)*(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)
=(1/2)*(1/1-1/11)
=5/11
1年前
2
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