某市2008年11月份曾发生流感,据统计,11月1日该市流感病毒新感染者有20人,此后,每天的新感染者平均比前一天的新感染者增加50人,由于该市医疗部门采取措施,使该种病毒的传播得到控制,从某天起,每天的新感染者平均比前一天的新感染者减少30人,到11月30日为止,该市在这30日内该病毒新感染者共有8 670人,问11月几日,该市新感染此病毒的人数最多?并求这一天的新感染人数.
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(文科做)已知向量
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=(cos
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x,sin
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x),
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=(cos
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,-sin
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),且
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,求:
①
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及|
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|;
②若f(x)=
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-2λ|
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|的最小值是
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,求实数λ的值.
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已知△ABC的内角A、B、C所对边分别为a,b,c,设向量
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,
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且
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的最大值.
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,n=1,2,3,….
(Ⅰ)证明:数列
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是等比数列;
(Ⅱ)求数列
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的前n项和S
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(1)当m=3时,求A∩(∁
RB);
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