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设数列(An)满足A0=0A1=2.且对一切n属于N.有An+2=2An+1-An+2.求An的通项公式

题目详情
设数列(An)满足A0=0 A1=2.且对一切n属于N.有An+2=2An+1-An+2.求An的通项公式
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答案和解析
a(n+2)=2a(n+1)-a(n) + 2
a(n+2)-a(n+1) = a(n+1) -a(n) +2
[a(n+2)-a(n+1)] -[a(n+1) -a(n)] =2
[a(n+1) -a(n)] - [a1-a0] = 2n
a(n+1) -a(n) = 2n+2
a(n)-a(n-1) = 2n
an - a1 = 4+6+8+..+2n
= (n+2)(n-1)
an = n^2+n