来自李光举的问题
用简便方法计算1/5*7+1/7*9+1/9*11+1/11*13+1/13*15
用简便方法计算1/5*7+1/7*9+1/9*11+1/11*13+1/13*15
1回答
2020-05-14 20:53
用简便方法计算1/5*7+1/7*9+1/9*11+1/11*13+1/13*15
用简便方法计算1/5*7+1/7*9+1/9*11+1/11*13+1/13*15
1/2×(1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13+1/13-1/15)
=1/2×(1/5-1/15)
=1/15