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科目:高中数学
来源:不详
题型:解答题
(本小题满分12分)
正项数列满足:
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,
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,点
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在圆
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上,
(1)求证:
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;
(2)若
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
,求证:数列

是等比数列;
(3)求和:
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科目:高中数学
来源:不详
题型:单选题
在等差数列

中,有

,则此数列的前13项之和为( )
A 24 B 39 C 52 D 104
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科目:高中数学
来源:不详
题型:单选题
已知数列

满足

,则

的值的( )
A.-6 | B.-3 | C.-1 | D. |
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科目:高中数学
来源:不详
题型:单选题
在等差数列{
an}中,若
a4+
a6+
a8+
a10+
a12=120,则2
a10-
a12的值为

(
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)
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