问题描述: 1/42+1/56+1/72+1/90+1/110=? 1个回答 分类:数学 2014-09-17 问题解答: 我来补答 1/42+1/56+1/72+1/90+1/110=1/(6×7)+1/(7×8)+1/(8×9)+1/(9×10)+1/(10×11)=1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11=1/6-1/11=5/66(请注意:1/42=1/(6×7)=1/6-1/7,后面方法相同.这是解题的关键) 展开全文阅读