设数列AN满足A1等于1,3(A1+a2+~+AN)=(n+2)an,求通向公式

问题描述:

设数列AN满足A1等于1,3(A1+a2+~+AN)=(n+2)an,求通向公式

an=n(n+1)/2 3(a1+a2+……+an)=(n+2)an3Sn = (n+2)an .(1)3S(n-1) = (n + 1)a(n-1).(2)(1)-(2)得:3an = (n+2)an - (n + 1)a(n-1)(n-1)an = (n + 1)a(n-1)an/a(n-1) = (n + 1)/(n-1)然后用你们肯定学过的累乘法:(a...