1 . 九连环是中国一种古老的智力游戏,其结构如图,玩九连环就是要把这九个环全部从框架上解下或套上.研究发现,要解下第
个环,则必须先解下前面第
个环.用
表示解下
个环所需最少移动次数,用
表示前
个环都已经解下后,再解下第
个环所需次数,显然,
,
,且
.若要将第
个环解下,则必须先将第
个环套回框架,这个过程需要移动
次,这时再移动1次,就可以解下第
个环;然后再将第
个环解下,又需要移动
次.由此可得,
.据此计算![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c2cd47b30a15a6ace20e2fc840a9add.png)
______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c05b9832b09731a574d4a4adf7448de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8c66acb7fc592b8474ab3f9d40a3590.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2e345e86daf74312a6992e5d1c3f47f5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/702353dcd94e65036a199deced89f8a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c0cdbf7b7cb42491810101c6e0db4ff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cd310a4c39f1522cafacf1aeae19c3c9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e181cdd42105f02e1a4446054ae65d34.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96ae7d749ab38b1b10e27a535719e673.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c0cdbf7b7cb42491810101c6e0db4ff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/908953401be1d145ed967572c8f6b753.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c0cdbf7b7cb42491810101c6e0db4ff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/908953401be1d145ed967572c8f6b753.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7c07ac0804045aca56d41c17ee80ae2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c2cd47b30a15a6ace20e2fc840a9add.png)
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2 . 我国古代数学著作《九章算术》中记载:斜解立方,得两堑堵.其意思是:一个长方体沿对角面一分为二,得到两个一模一样的堑堵.如图,在长方体
中,
,
,
,将长方体
沿平面
一分为二,得到堑堵
,下列结论正确的序号为______ .
①点C到平面
的距离等于
;
②
与平面
所成角的正弦值为
;
③堑堵
外接球的表面积为
;
④堑堵
没有内切球.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/efc6e4b936d7a800e839a30c3839574d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e65a3e478bb87d094e3a0af30dd10ae8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1f3e58edd1f900ca82bb2a3058293f52.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/679748eab882a6be0fefd2cc300349a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b5b14d74bdf9ed7c45b2e754b7ccc4f.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/4/2/203cf047-3c7e-43ff-9a8e-fb0157d5f7d4.png?resizew=233)
①点C到平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/679748eab882a6be0fefd2cc300349a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81365a3726621b6557bd26f3a1a51cae.png)
②
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/588eb9393564a33552c4b2e8de837ca5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15a24acb11fac4bcf6a86e3e9223a48b.png)
③堑堵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b5b14d74bdf9ed7c45b2e754b7ccc4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f08a01aed02ce1eaf1aaefaa0342b7ad.png)
④堑堵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b5b14d74bdf9ed7c45b2e754b7ccc4f.png)
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3 . 已知函数![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c84496f87abcf6d9c51c25391d6f55d7.png)
,
,给出下列四个结论:
①函数
在区间
上单调递减;
②函数
的最大值是
;
③若关于
的方程
有且只有一个实数解,则
的最小值为
;
④若对于任意实数a,b,不等式
都成立,则
的取值范围是
.
其中所有正确结论的序号是_______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c84496f87abcf6d9c51c25391d6f55d7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dcd9218a657b17654c5d757a6f7dee9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8ba56d22e9f7803b5545f91e1e0c2a62.png)
①函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f86f37ec8e15846bd731ab4fcdbacd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccfdd3d02b54e997cbec983d80f6bafd.png)
②函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4669810732b633b60dbeaf0bf57204f6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f89eef3148f2d4d09379767b4af69132.png)
③若关于
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c0008d46dc238d710a1efe7e2c17237.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f89eef3148f2d4d09379767b4af69132.png)
④若对于任意实数a,b,不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0dec45d8c4760288f233275bdfcae96.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19094cbb9d60021934728b1d3daf8a9b.png)
其中所有正确结论的序号是
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