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[数列] 一眼看尽等差数列前12项和

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isee posted 2021-8-3 21:26 |Read mode

已知公差不为0的等差数列$\left\{ a_n \right\}$满足\(a_5^2+a_6^2=a_7^2+a_8^2\)，则\(S_{12}\)=______ .

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其妙 posted 2021-8-3 22:01

$a_5+a_6+a_7+a_8=0$，所以，$S_{12}=0$

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