1-1/6+1/42+1/56+1/72 要用简便方法计算

问题描述:

1-1/6+1/42+1/56+1/72 要用简便方法计算

=1-1/6+1/6*7+1/7*8+1/8*9
=1-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1-1/9
=8/9