数列{an}得通项公式为an=1/（4n-3）（4n+1)求sn_数学解答

数列{an}得通项公式为an=1/（4n-3）（4n+1)求sn

人气：220 ℃　时间：2020-02-06 01:02:45

解答

An=1/(4n-3)(4n+1)=[1/(4n-3)-1/(4n+1)]/4
Sn=[1-1/5+1/5-1/9+...+1/(4n-7)-1/(4n-3)+1/(4n-3)-1/(4n+1)]/4
=[1-1/(4n+1)]/4
=n/(4n+1)