早教吧作业答案频道 -->数学-->
求数列1/(1×5),1/(5×9),…,1/(4n-3)(4n+1)的前n项和
题目详情
▼优质解答
答案和解析
sn=1/(1*5)+ 1/(5*9)+.+1/(4n-3)(4n+1)=1/4*(1-1/5)+1/4*(1/5-1/9)+.+1/4*[1/(4n-3)-1/(4n+1)]=1/4*[1-1/5+1/5-1/9+.+1/(4n-3)-1/(4n+1)]=1/4*[1-1/(4n+1)]=1/4*4n/(4n+1)=n/(4n+1)
看了 求数列1/(1×5),1/(...的网友还看了以下：