已知数列{an}的前n和为Sn,且Sn=2an+n^2-3n-2 n为正整数求证:1数列是等比数列2设bn=an*cosn180度,求数列bn的前n项和p
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![已知数列{an}的前n和为Sn,且Sn=2an+n^2-3n-2 n为正整数求证:1数列是等比数列2设bn=an*cosn180度,求数列bn的前n项和p](/uploads/image/z/1740905-17-5.jpg?t=%E5%B7%B2%E7%9F%A5%E6%95%B0%E5%88%97%7Ban%7D%E7%9A%84%E5%89%8Dn%E5%92%8C%E4%B8%BASn%2C%E4%B8%94Sn%3D2an%2Bn%5E2%EF%BC%8D3n%EF%BC%8D2+n%E4%B8%BA%E6%AD%A3%E6%95%B4%E6%95%B0%E6%B1%82%E8%AF%81%EF%BC%9A1%E6%95%B0%E5%88%97%E6%98%AF%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%972%E8%AE%BEbn%3Dan%2Acosn180%E5%BA%A6%2C%E6%B1%82%E6%95%B0%E5%88%97bn%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8Cp)
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