由于|1/n-1/(n+1)|=1/n-1/(n+1),n大于0. 故原式=1/10-1/11+1/11-1/12+......+1/98-1/99+1/99-1/100=1/10-1/100=9/100
|1/10-1/11|+|1/11-1/12|+....+|1/99-1/100|=1/10-1/11+1/11-1/12+……+1/99-1/100=1/10-1/100=10/100-1/100=9/100