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    (6)在等比数列的值为 (A) 9 (B) 1 (C)2 (D)3 【查看更多】

     

    题目列表(包括答案和解析)

     在等比数列的值为（  ）

    A．1          B．2            C．3            D． 9

     

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    在等比数列的值为（    ）                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                

        A.9           B．1  C．2    D．3

     

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    在等比数列的值为（    ）                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                

        A.9           B．1  C．2    D．3

     

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    在等比数列的值为 （   ）

        A．1            B．2                C．3                D． 9  

     

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    在等比数列的值为  （    ）

           A．9                B．1                C．2         D．3

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        2009.3

    一、选择题

    （1）B  （2）A  （3）B （4）C （5）B （6）D

    （7）D   （8）C  （9）C （10）B （11）A （12）C

    二、填空题

    1,3,5

    三、解答题

    （17）解:（Ⅰ）-             ---------------------------2分

    高三年级人数为-------------------------3分

    现用分层抽样的方法在全校抽取48名学生，应在高三年级抽取的人数为

    (人).                       --------------------------------------6分

    （Ⅱ）设“高三年级女生比男生多”为事件，高三年级女生、男生数记为.

    由（Ⅰ）知且

    则基本事件空间包含的基本事件有

    共11个,     ------------------------------9分

    事件包含的基本事件有

    共5个   

                    --------------------------------------------------------------11分

    答：高三年级女生比男生多的概率为.  …………………………………………12分

    （18）解：（Ⅰ）  …………2分

    在中，由于，

                                            …………3分

    又，

                           

    又，所以，而，因此.…………6分

       （Ⅱ）由，

    由正弦定理得                                …………8分

    ，

    即，由（Ⅰ）知，所以    …………10分

    由余弦弦定理得 ，     …………11分

    ，

                                                   …………12分

    （19）（Ⅰ）证明：∵、分别为、的中点，∴.

         又∵平面平面

    ∴平面                                         …………4分

    （Ⅱ）∵，，∴平面.

    又∵，∴平面.

    ∵平面,∴平面平面.               …………8分

    （Ⅲ）∵平面，∴是三棱锥的高.

    在Rt△中，.

        在Rt△中，.

     ∵，是的中点，

    ∴,

    故.        ………………12分

    （20）解：（Ⅰ）依题意得

                                 …………2分

     解得，                                             …………4分

    .       …………6分

       （Ⅱ）由已知得，                  …………8分

                                                             ………………12分

    （21）解：（Ⅰ）

          令=0,得                        ………2分

    因为，所以可得下表：

    0

    +

    0

    -

    ㄊ

    极大

    ㄋ

                                                              ………………4分

    因此必为最大值,∴，因此，

         ，

        即，∴，

     ∴                                       ……………6分

    （Ⅱ）∵，∴等价于， ………8分

     令，则问题就是在上恒成立时，求实数的取值范围，为此只需，即，                 …………10分

    解得，所以所求实数的取值范围是[0，1].            ………………12分

    （22）解:（Ⅰ）由得，，

    所以直线过定点（3，0），即.                       …………………2分

     设椭圆的方程为,

    则,解得，

    所以椭圆的方程为.                    ……………………5分

    （Ⅱ）因为点在椭圆上运动,所以，      ………………6分

    从而圆心到直线的距离

    所以直线与圆恒相交.                             ……………………9分

    又直线被圆截得的弦长

    ，       …………12分

    由于,所以,则,

    即直线被圆截得的弦长的取值范围是.  …………………14分

     

     

     


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