等比数列{an}满足a1+a3=3a2,且a2+2是a2与a4的等差中项①求{an}的通项公式 ②bn=an-log以2为底an,.②bn=an-log以2为底an,Sn=b1+b2+b3····+bn,求不等式Sn-2^(n+1)+47是2a1+a3=3a2
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![等比数列{an}满足a1+a3=3a2,且a2+2是a2与a4的等差中项①求{an}的通项公式 ②bn=an-log以2为底an,.②bn=an-log以2为底an,Sn=b1+b2+b3····+bn,求不等式Sn-2^(n+1)+47是2a1+a3=3a2](/uploads/image/z/13428880-16-0.jpg?t=%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%7Ban%7D%E6%BB%A1%E8%B6%B3a1%2Ba3%3D3a2%2C%E4%B8%94a2%2B2%E6%98%AFa2%E4%B8%8Ea4%E7%9A%84%E7%AD%89%E5%B7%AE%E4%B8%AD%E9%A1%B9%E2%91%A0%E6%B1%82%7Ban%7D%E7%9A%84%E9%80%9A%E9%A1%B9%E5%85%AC%E5%BC%8F+%E2%91%A1bn%3Dan-log%E4%BB%A52%E4%B8%BA%E5%BA%95an%2C.%E2%91%A1bn%3Dan-log%E4%BB%A52%E4%B8%BA%E5%BA%95an%2CSn%3Db1%2Bb2%2Bb3%C2%B7%C2%B7%C2%B7%C2%B7%2Bbn%2C%E6%B1%82%E4%B8%8D%E7%AD%89%E5%BC%8FSn-2%5E%EF%BC%88n%2B1%EF%BC%89%2B47%E6%98%AF2a1%2Ba3%3D3a2)
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等比数列{an}满足a1+a3=3a2,且a2+2是a2与a4的等差中项①求{an}的通项公式 ②bn=an-log以2为底an,.②bn=an-log以2为底an,Sn=b1+b2+b3····+bn,求不等式Sn-2^(n+1)+47是2a1+a3=3a2
等比数列{an}满足a1+a3=3a2,且a2+2是a2与a4的等差中项①求{an}的通项公式 ②bn=an-log以2为底an,.
②bn=an-log以2为底an,Sn=b1+b2+b3····+bn,求不等式Sn-2^(n+1)+47
是2a1+a3=3a2
等比数列{an}满足a1+a3=3a2,且a2+2是a2与a4的等差中项①求{an}的通项公式 ②bn=an-log以2为底an,.②bn=an-log以2为底an,Sn=b1+b2+b3····+bn,求不等式Sn-2^(n+1)+47是2a1+a3=3a2
an=2^n
bn=an-n
Sn=S(an)-n(n+1)/2=2(2^n-1)-n(n+1)/2=2^(n+1)-2-n(n+1)/2
Sn-2^(n+1)+47=45-n(n+1)/290
得n最小为10
第一问我已经求出:an=2^n 。
你求错了
照你说的
a1=2
a2=4
a3=8
你觉得满足a1+a3=3a2吗?
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