来自乔旭峰的问题
2/(1*2*3)+2/(2*3*4)+2/(3*4*5).+2/(28*29*30)
2/(1*2*3)+2/(2*3*4)+2/(3*4*5).+2/(28*29*30)
1回答
2019-08-01 02:46
2/(1*2*3)+2/(2*3*4)+2/(3*4*5).+2/(28*29*30)
2/(1*2*3)+2/(2*3*4)+2/(3*4*5).+2/(28*29*30)
2/(1*2*3)+2/(2*3*4)+2/(3*4*5).+2/(28*29*30)
=(1/1*2-1/2*3)+(1/2*3-1/3*4)+(1/3*4-1/4*5)+...+(1/28*29-1/29*30)
=1/1*2-1/29*30
=1/2-1/870
=434/870
=217/435