=1+1/2-3+1/6+3+1/12-5+1/20+5+1/30-7+1/42+7+1/56—9+1/72+9+1/10
=（1-3+3-5+5-7+7-9+9）+（1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90）
=1+1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10
=2-1/10
=19/10哦，我懂了~~