8. 在数列.是各项均为正数的等比数列.设. (Ⅰ)数列是否为等比数列?证明你的结论, (Ⅱ)设数列.的前项和分别为..若..求数列的前项和. 解:(Ⅰ)是等比数列.························································································· 2分 证明:设的公比为.的公比为.则 .故为等比数列.············································ 5分 (Ⅱ)数列和分别是公差为和的等差数列. 由条件得.即 .····················································································· 7分 故对..-. . 于是 将代入得...································································· 10分 从而有. 所以数列的前项和为 .······················································································ 12分 查看更多

 

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(本小题满分12分)在数列是各项均为正数的等比数列,设.(Ⅰ)数列是否为等比数列?证明你的结论;(Ⅱ)设数列的前项和分别为.若,求数列的前项和.

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(本小题满分12分)在数列是各项均为正数的等比数列,设.(Ⅰ)数列是否为等比数列?证明你的结论;(Ⅱ)设数列的前项和分别为.若,求数列的前项和.

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(本小题满分12分)在数列是各项均为正数的等比数列,设.(Ⅰ)数列是否为等比数列?证明你的结论;(Ⅱ)设数列的前项和分别为.若,求数列的前项和.

 

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(本小题满分12分)在数列是各项均为正数的等比数列,设.(Ⅰ)数列是否为等比数列?证明你的结论;(Ⅱ)设数列的前项和分别为.若,求数列的前项和.

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5、已知数列an是各项均为正数的等差数列,且公差不为0,则以下各式中一定正确的为(  )

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