1/15+1/35+1/63+1/99+1/143+1/195用裂项做

问题描述:

1/15+1/35+1/63+1/99+1/143+1/195用裂项做

裂项法:
1/15+1/35+1/63+1/99+1/143+1/195
=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)
=1/2×(1/3-1/15)
=1/2×4/15
=2/15