提问:1x1/2+1/2x1/3+1/3x1/4+1/4x1/5+1/5x1/6+1/6x1/7 用简便方法

提问:1x1/2+1/2x1/3+1/3x1/4+1/4x1/5+1/5x1/6+1/6x1/7 用简便方法
提问:1x1/2+1/2x1/3+1/3x1/4+1/4x1/5+1/5x1/6+1/6x1/7 用简便方法

提问:1x1/2+1/2x1/3+1/3x1/4+1/4x1/5+1/5x1/6+1/6x1/7 用简便方法
1x1/2+1/2x1/3+1/3x1/4+1/4x1/5+1/5x1/6+1/6x1/7
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/9-1/7
=1-1/7
=6/7