1 . 在用反证法证明命题“若三个正数a,b,c满足
,则a,b,c三个数中至多有两个数小于3”时,应该反设为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/724e3ffa8bf693be79f047bc77474a84.png)
A.假设a,b,c三个数都小于3 |
B.假设a,b,c三个数都大于3 |
C.假设a,b,c三个数中至少有两个数小于3 |
D.假设a,b,c三个数中至多有两个数不小于3 |
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2022-05-09更新
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3卷引用:河南宋基信阳实验中学2021-2022学年高二下学期转段考试(升高三)理科数学试题
解题方法
2 . (1)已知a,b,c是不全相等的正数,求证:
;
(2)用反证法证明:若函数
在区间
上是增函数,则方程
在区间
上至多只有一个实数根.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a9ab8d8a251e0ec8d0e21a8f2372ef78.png)
(2)用反证法证明:若函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f86f37ec8e15846bd731ab4fcdbacd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f030c36bb8786df88d401792062a4100.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/86b92b70365c63607daecdc8deb73ecf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f030c36bb8786df88d401792062a4100.png)
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名校
3 . 用反证法证明命题“自然数
,
,
中至少有一个偶数”,则证明的第一步,其正确的反设为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/071a7e733d466949ac935b4b8ee8d183.png)
A.![]() ![]() ![]() | B.![]() ![]() ![]() |
C.![]() ![]() ![]() | D.![]() ![]() ![]() |
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2021-08-11更新
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2卷引用:河南省信阳市2020-2021学年高二下学期期末数学(理)试题
4 . 求证:当
时,
,
,
不可能成等差数列.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac69e6db1df13ed64756b4f391ae9fac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d249094ecb996458e35182d6b461299.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/79359410e01b6f4afec08935927e2671.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d498a3d8f4f242a7fe402d6cadea5fd7.png)
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2020-04-25更新
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200次组卷
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3卷引用:河南省信阳市2021-2022学年高二下学期期中教学质量检测数学(文科)试题
5 . (1)用综合法证明:
,
,
均为正实数);
(2)已知:
,
,
,求证:
,
中至少有一个不小于
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54cfb2a3446d8011b89d87fba03a20e4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/071a7e733d466949ac935b4b8ee8d183.png)
(2)已知:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eb63478132d4c1fef3c17e591919da83.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/25d6b6b86228a9b721d618fae2963e57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bd86a39ae4fb080287cda63e4a68266.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c95b6be4554f03bf496092f1acdfbb89.png)
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