小学数学///

一1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
=1/2+1/2-1/3+1/3-1/4+1/4-1/5.............+1/7-1/8
=1-1/8
=7/8
二 .2/3+1/4+2/15+1/12+2/35+1/24
=2/3+1/4+1/3-1/5+1/3-1/4+1/5-1/7+1/24
=2/3+1/3+1/3+1/4-1/4+1/5-1/5-1/7+1/24
=1+1/3-1/7+1/24
=1+56/168-24/168+7/168
=1+39/168
=1+13/56

一：8/9 二:69/56
一:1/2+1/2-1/3+1/3-1/4+1/4-1/5......+1/8-1/9=8/9

错了不能怪我哦

一：8/9 二:69/56
一:1/2+1/2-1/3+1/3-1/4+1/4-1/5......+1/8-1/9=8/9

69/56