1/3+1/15+1/35+1/63+1/99+1/143+1/195+1/255 +1/323+1/399=
问题描述:
1/3+1/15+1/35+1/63+1/99+1/143+1/195+1/255 +1/323+1/399=
答
1/3+1/15+1/35+1/63+1/99+1/143+1/195+1/255 +1/323+1/399=1/2×(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13+1/13-1/15+1/15-1/17+1/17-1/19+1/19-1/21)=1/2×(1-1/21)=1/2×20/21=10/21...