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发表于:2019-10-13
问题详情:已知椭圆C:的离心率为,且过点A(2,1).若P,Q是椭圆C上的两个动点,且使∠PAQ的角平分线总垂直于x轴.(1)求椭圆的方程(2)试判断直线PQ的斜率是否为定值?若是,求出该值;若不是,请说明理由.【回答...
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发表于:2020-02-25
问题详情:阅读下面短文,从每题所给的三个选项(A、B和C)中,选出最佳选项。DuYijun,a21-year-oldFudanUniversitystudent,wasoneofthe36peoplewhodiedinthecrushonNewYear’sEveontheBund(外...
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发表于:2020-08-18
问题详情:选择填空—CanyoubelievethatNingZetao,a21-year-oldboy,wonthefirstprizeintheswimmingcompetitioninInchonAsianGames?—Ihaveheardthat.Hisparentsmustbesoproudandhappywi...
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发表于:2019-10-31
问题详情:.已知数列{an}为等差数列,a7﹣a2=10,且a1,a6,a21依次成等比数列.(1)求数列{an}的通项公式;(2)设bn,数列{bn}的前n项和为Sn,若Sn,求n的值.【回答】(1)an=2n+3(2)10【解析】【分析】(1)设等差数列的公差...