1-1/6+1/42+1/56+1/72
=1-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1-1/9
=8/9这是什么意思？1/42=1/6-1/71/56=1/7-1/81/72=1/8-1/9谢了！我才读小学！