1/(12×13)+1/(13×14)+……+1/(19×20)的值为: A.1/1 发布时间:2017-07-20 22:27 │ 来源:www.tikuol.com 题型:单项选择题 问题: 1/(12×13)+1/(13×14)+……+1/(19×20)的值为:A.1/12 B.1/20 C.1/30D.1/40