如题所述
5/1*3+5/3*5+5/5*7+5/7*9+5/9*11+5/11*3
=5×1/2×【1/(1×3)+1/(3×5)+1/(5×7)+1/(7×9)+1/(9×11)+1/(11×13)】
=5/2×【1-1/3+1/3-1/5+……+1/11-1/13】
=5/2×【1-1/13】
=5/2×12/13
=30/13
=5×1/2×【1/(1×3)+1/(3×5)+1/(5×7)+1/(7×9)+1/(9×11)+1/(11×13)】
=5/2×【1-1/3+1/3-1/5+……+1/11-1/13】
=5/2×【1-1/13】
=5/2×12/13
=30/13
温馨提示:答案为网友推荐,仅供参考
第1个回答 2011-09-20
最后一个应该是5/11*13吧
5/1*3+5/3*5+5/5*7+5/7*9+5/9*11+5/11*13
=(5/2)×(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13)
=(5/2)×(1-1/13)
=(5/2)×12/13
=30/13
祝你开心
5/1*3+5/3*5+5/5*7+5/7*9+5/9*11+5/11*13
=(5/2)×(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13)
=(5/2)×(1-1/13)
=(5/2)×12/13
=30/13
祝你开心