题目

1x2/1+2x3/1+3x4/1+4x5/1+5x6/1+6x7/1
题打错了，正确的是1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7

提问时间：2020-09-26

答案

1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=6/7
因为1/1*2=1-1/2同理..