递等式计算 1/42+1/56+1/72+1/90+1/110

问题描述:

递等式计算 1/42+1/56+1/72+1/90+1/110

1/42+1/56+1/72+1/90+1/110
=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