1.已知等差数列{an}的前n项和Sn,若OB=a1·OA+a200·OC,且A、B、C三点共线(该直线不过原点),则S200=?(OB,OA,是向量)2.等比数列{an}的前n项积记为Mn,M10=20,M20=10,M30=?3.数列{an}是正项等比数列,{bn}是等差
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![1.已知等差数列{an}的前n项和Sn,若OB=a1·OA+a200·OC,且A、B、C三点共线(该直线不过原点),则S200=?(OB,OA,是向量)2.等比数列{an}的前n项积记为Mn,M10=20,M20=10,M30=?3.数列{an}是正项等比数列,{bn}是等差](/uploads/image/z/5426013-21-3.jpg?t=1.%E5%B7%B2%E7%9F%A5%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%7Ban%7D%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8CSn%2C%E8%8B%A5OB%3Da1%C2%B7OA%2Ba200%C2%B7OC%2C%E4%B8%94A%E3%80%81B%E3%80%81C%E4%B8%89%E7%82%B9%E5%85%B1%E7%BA%BF%EF%BC%88%E8%AF%A5%E7%9B%B4%E7%BA%BF%E4%B8%8D%E8%BF%87%E5%8E%9F%E7%82%B9%EF%BC%89%2C%E5%88%99S200%3D%3F%EF%BC%88OB%2COA%2C%E6%98%AF%E5%90%91%E9%87%8F%EF%BC%892.%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%7Ban%7D%E7%9A%84%E5%89%8Dn%E9%A1%B9%E7%A7%AF%E8%AE%B0%E4%B8%BAMn%2CM10%3D20%2CM20%3D10%2CM30%3D%3F3.%E6%95%B0%E5%88%97%7Ban%7D%E6%98%AF%E6%AD%A3%E9%A1%B9%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%2C%7Bbn%7D%E6%98%AF%E7%AD%89%E5%B7%AE)
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