1/6+1/12+1/20+1/30+1/42+1/561/8+1/24+1/48+1/80+1/120

1/6+1/12+1/20+1/30+1/42+1/561/8+1/24+1/48+1/80+1/120
1/6+1/12+1/20+1/30+1/42+1/56
1/8+1/24+1/48+1/80+1/120

1/6+1/12+1/20+1/30+1/42+1/561/8+1/24+1/48+1/80+1/120
(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)=1/2-1/8=3/8=0.375
1/8+1/8*1/3+1/8*1/6+1/8*1/10+1/8*1/15
=1/8*(1+1/3+1/6+1/10+1/15)
=1/8*5/3
=5/24

第一题=1/2-1/3+1/3-1/4+....1/7-1/8=3/8,第二题=1/2(1/2-1/4+1/4-1/6...+1/10-1/12)=5/24