30*(1/15+1/35+1/63+1/99+1/143+1/195)=
问题描述:
30*(1/15+1/35+1/63+1/99+1/143+1/195)=
答
1/15=1/3-1/5;1/35=1/5-1/7;同理可得~最后一项是1/13-1/15~30*(1/3.........-1/15)=8/15
30*(1/15+1/35+1/63+1/99+1/143+1/195)=
1/15=1/3-1/5;1/35=1/5-1/7;同理可得~最后一项是1/13-1/15~30*(1/3.........-1/15)=8/15