等差数列.公差为d.前n项合为Sn=-n²,则通项公式和公差分别为?
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等差数列.公差为d.前n项合为Sn=-n²,则通项公式和公差分别为?
等差数列.公差为d.前n项合为Sn=-n²,则通项公式和公差分别为?
等差数列.公差为d.前n项合为Sn=-n²,则通项公式和公差分别为?
Sn=-n²
所以
通项:an=sn-s(n-1)=-n²+(n-1)²=-2n+1
公差d=-2
等差数列.公差为d.前n项合为Sn=-n²,则通项公式和公差分别为?
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