已知数列{an},a1=2,an+1=an+2n,则数列的通项公式an=?

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已知数列{an},a1=2,an+1=an+2n,则数列的通项公式an=?
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已知数列{an},a1=2,an+1=an+2n,则数列的通项公式an=?
已知数列{an},a1=2,an+1=an+2n,则数列的通项公式an=?

已知数列{an},a1=2,an+1=an+2n,则数列的通项公式an=?
an+1=an+2n
推出
an=an-1+2(n-1)
.
.
.
a2=a1 + 2
累加得
an = a1 + 2(2+3+4+...n-1)
an = 2 + n(n-1)
an = n^2 - n+2 (n>=1)

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