数列】 (1 19:1:12)已知数列{an}是等差数列,数列{bn}是各项均为正数的等比数列,a1=b1=1,且a4+b4=15,a7+b7=77.(2)设数列{an*bn}的前n项和为Sn,求满足n*2n+1-Sn>90的最小正整数n
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![数列】 (1 19:1:12)已知数列{an}是等差数列,数列{bn}是各项均为正数的等比数列,a1=b1=1,且a4+b4=15,a7+b7=77.(2)设数列{an*bn}的前n项和为Sn,求满足n*2n+1-Sn>90的最小正整数n](/uploads/image/z/119888-8-8.jpg?t=%E6%95%B0%E5%88%97%E3%80%91+%281+19%3A1%3A12%29%E5%B7%B2%E7%9F%A5%E6%95%B0%E5%88%97%7Ban%7D%E6%98%AF%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%2C%E6%95%B0%E5%88%97%7Bbn%7D%E6%98%AF%E5%90%84%E9%A1%B9%E5%9D%87%E4%B8%BA%E6%AD%A3%E6%95%B0%E7%9A%84%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%2Ca1%3Db1%3D1%2C%E4%B8%94a4%2Bb4%3D15%2Ca7%2Bb7%3D77.%282%29%E8%AE%BE%E6%95%B0%E5%88%97%7Ban%2Abn%7D%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8C%E4%B8%BASn%2C%E6%B1%82%E6%BB%A1%E8%B6%B3n%2A2n%2B1-Sn%3E90%E7%9A%84%E6%9C%80%E5%B0%8F%E6%AD%A3%E6%95%B4%E6%95%B0n)
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