2024·全国·模拟预测
解题方法
1 . 在解决问题“已知正实数
满足
,求
的取值范围”时,可通过重新组合,利用基本不等式构造关于
的不等式,通过解不等式求范围.具体解答如下:
由
,得
,即
,解得
的取值范围是
.
请参考上述方法,求解以下问题:
已知正实数
满足
,则
的取值范围是______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0fffbec1fe851795dfdd448bf0d165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb975603433961a27ff01c734d39575f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f29d5f376c75c41ae6af0c8a8565449.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f29d5f376c75c41ae6af0c8a8565449.png)
由
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d14a76fbd7733394b3a7a8c7508ae8f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09a2ebb75f6dc5ba596a98ccbc2bb9be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef066cf9a851361e923ed40c97b842.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f29d5f376c75c41ae6af0c8a8565449.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eed05aa46ec16ee8f98272565d2a2ed9.png)
请参考上述方法,求解以下问题:
已知正实数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0fffbec1fe851795dfdd448bf0d165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb975603433961a27ff01c734d39575f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4e7bf9200b351a259ddfc6c0266129d.png)
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2 . 阅读理解:高斯上小学时,有一次数学老师让同学们计算“从1到100这100个正整数的和”.许多同学都采用了依次累加的计算方法,计算起来非常烦琐,且易出错.聪明的小高斯经过探索后,给出了下面漂亮的解答过程.
解:设
①,则
②,
①+②,得
.
(两式左右两端分别相加,左端等于2S,右端等于100个101的和)
所以
,
③,所以
.
后来人们将小高斯的这种解答方法概括为“倒序相加法”
计算:
= _____ .
解:设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/45d05f7125540086a961efd2afddb588.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4663fd551144091fcd826a6ecd7a9603.png)
①+②,得
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6800c25d59d4bf730f469ce16412a7fe.png)
(两式左右两端分别相加,左端等于2S,右端等于100个101的和)
所以
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d46540f510d1f3537e0453ebb1bd6e9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/da9c674c761493e544d7af9bb5046a86.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4ac52232d822e91ac25df49702ba8c71.png)
后来人们将小高斯的这种解答方法概括为“倒序相加法”
计算:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24d7c6e74c5501a04785b710ffe91ec6.png)
您最近一年使用:0次
3 . 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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4 . 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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