7．在等比數(shù)列的值為 A．9 B．1 C．2 D．3 【查看更多】

 

題目列表(包括答案和解析)

 在等比數(shù)列的值為（  ）

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

 

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在等比數(shù)列的值為（    ）                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                

    A.9           B．1  C．2    D．3

 

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在等比數(shù)列的值為（    ）                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                

    A.9           B．1  C．2    D．3

 

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在等比數(shù)列的值為 （   ）

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

 

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在等比數(shù)列的值為  （    ）

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

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一、選擇題：

1．A              2.A             3.D           4.C

5.B               6.D             7.D           8.B

9.C               10.C            11.D          12.C

二、填空題：

13.-252     14.      15.  -3       16.         17.

三、解答題：

18解：（1）6ec8aac122bd4f6e 

6ec8aac122bd4f6e

（2）由題設(shè)，6ec8aac122bd4f6e

6ec8aac122bd4f6e 

19解：（1）記“第一次與第二次取到的球上的號碼的和是4”為事件A，則

6ec8aac122bd4f6e 

所以第一次與第二次取到的地球上的號碼的和是4的概率6ec8aac122bd4f6e

（2）記“第一次與第二次取到的上的號碼的積不小于6”為事件B，則

6ec8aac122bd4f6e 

錯誤！嵌入對象無效。

20解法一：（1）∵E，F(xiàn)分別是AB和PB的中點，

∴EF∥PA 

又ABCD是正方形，∴CD⊥AD，

由PD⊥底面ABCD得CD⊥PD，CD⊥面PAD，

∴CD⊥PA，∴EF⊥CD。

（2）設(shè)AB=a，則由PD⊥底面ABCD及ABCD是正方形可求得

∴DB與平面DEF所成的角是6ec8aac122bd4f6e

（3）在平面PAD內(nèi)是存在一點G，使G在平面PCB

上的射影為△PCB的外心，

G點位置是AD的中點。 

證明如下：由已知條件易證

Rt△PDG≌Rt△CDG≌Rt△BAG，

∴GP=GB=GC，即點G到△PBC三頂點的距離相等。

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        解法二：以DA，DC，DP所在直線分別為x軸，y軸，z軸建立空間直角坐標系（如圖）。

        6ec8aac122bd4f6e

        （1）6ec8aac122bd4f6e

        6ec8aac122bd4f6e 

        （2）設(shè)平面DEF的法向量為6ec8aac122bd4f6e

        6ec8aac122bd4f6e

        （3）假設(shè)存在點G滿足題意

        6ec8aac122bd4f6e

        21解：（1）設(shè)6ec8aac122bd4f6e

        6ec8aac122bd4f6e

        （2）6ec8aac122bd4f6e

        6ec8aac122bd4f6e

        22解：（1）令6ec8aac122bd4f6e

        而6ec8aac122bd4f6e 

        （2）設(shè)6ec8aac122bd4f6e

        6ec8aac122bd4f6e

        （3）由6ec8aac122bd4f6e

        ∴不等式化為6ec8aac122bd4f6e 

        由（2）已證6ec8aac122bd4f6e …………7分

        ①當6ec8aac122bd4f6e

        6ec8aac122bd4f6e

        ②當6ec8aac122bd4f6e不成立，∴不等式的解集為6ec8aac122bd4f6e …………10分

        ③當6ec8aac122bd4f6e，

        6ec8aac122bd4f6e

        23解：（1）6ec8aac122bd4f6e  …………1分

        6ec8aac122bd4f6e

          （2）設(shè)6ec8aac122bd4f6e

        6ec8aac122bd4f6e

        ①當6ec8aac122bd4f6e

        6ec8aac122bd4f6e

        ②當6ec8aac122bd4f6e

        6ec8aac122bd4f6e

         


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