|1/11-1/11|+|1/11-1/12|+|1/13-1/12|＝1/11-1/11+1/11-1/12+1/12-1/13＝1/11-1/13＝2/143|1/3-1/2|+|1/4-1/3|+|1/5-1/4|+……+|1/10-1/9| ＝1/2-1/3-1/3+1/4-1/4+1/5+……1/9-1/9+1/10＝1/2+1/10＝6/10＝3/5...