来自李延磊的问题
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=?用简便算法算
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=?用简便算法算
1回答
2020-05-31 05:58
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=?用简便算法算
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=?用简便算法算
1/6=1/2-1/3
1/12=1/3-1/4
1/20=1/4-1/5
1/30=1/5-1/6
1/42=1/6-1/7
=1/7-1/8
=1/8-1/9
=1/9-1/10
所以原式=1/2+1/2-1/10
=9/10