1/42+1/56+1/72+1/90+1/110这种题怎么做
问题描述:
1/42+1/56+1/72+1/90+1/110这种题怎么做
答
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中间全部抵消
=5/66