全民奇迹 金币共用吗:数列{An}满足A1+2A2+3A3+4A4+``````+nAn=n(n+1)(n+2),那么这数列的通式是?
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n属于N
a1+2a2+...+(n-1)a<n-1>=(n-1)n(n+1)
A1+2A2+3A3+4A4+``````+nAn=n(n+1)(n+2)
所以
nAn=n*(n+1)*3
所以An=(n+1)*3
An=3(n+1)
nSn= a1+2a2+3a3+......+nan (1)
(n+1)Sn=2a1+3a3+4a3+......+(n+1)an (2)
(2)-(1)就能算出an
An=3*(n+1)
数列{An}满足A1+2A2+3A3+4A4+``````+nAn=n(n+1)(n+2),那么这数列的通式是?
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