数列{an}满足:a1=2,an=an-1+2n-1(n≥2),则该数列的通项公式是 ___ .
人气:121 ℃ 时间:2020-01-31 08:56:18
解答
∵数列{a
n}满足:a
1=2,a
n=a
n-1+2n-1(n≥2),
∴a
n-a
n-1=2n-1(n≥2),
∴a
n=a
1+a
2-a
1+a
3-a
2+…+a
n-a
n-1=2+3+5+7+…+(2n-1)
=2+
=n
2+1.
故答案为:
an=n2+1.
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