2/15+2/35+2/63+2/99+2/143

分类: 作业答案 • 2022-04-28 20:13:55

问题描述：

答

2/15+2/35+2/63+2/99+2/143
=2/3x5+2/5x7+2/7x9+2/9x11+2/11x13
=1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13
=1/3-1/13
=10/39