1/3+1/15+/135+1/63+1/99
问题描述:
1/3+1/15+/135+1/63+1/99
答
1/3+1/15+1/35+1/63+1/99=【(1-1/3)+(1/3-1/5)+(1/5-1/7)+(1/7-1/9)+(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=【1-1/11】*1/2=10/11*1/2=5/11