名校
解题方法
1 . 在解决问题:“证明数集
没有最小数”时可用反证法证明:
假设
是
中的最小数,则存在
,
可得:
,与假设中“a是A中的最小数”矛盾,
所以数集
没有最小数.
那么对于问题:“证明数集![](https://staticzujuan.xkw.com/quesimg/Upload/formula/148c4902eb8e6a73046dedab761e3abf.png)
,并且
没有最大数”,也可以用反证法证明:我们可以假设
是
中的最大数,则存在
,且
,其中
的一个值可以是__________ (用
、
表示),由此可知,与假设
是
中的最大数矛盾.所以数集
没有最大数.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/79950aacd93566f38d8e16021d2eb23b.png)
假设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/abc7dff3ffdad01a473cc8bdb236f2d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0914b68f106a912420705b2f3928ca42.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a2710435ef4f66f24a0f4b67d7e83f0e.png)
可得:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54bfb810e811cb3d9482e2ec0d8db742.png)
所以数集
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/79950aacd93566f38d8e16021d2eb23b.png)
那么对于问题:“证明数集
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/148c4902eb8e6a73046dedab761e3abf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eb45566dd4ac7dd3524acdb890c29bb6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f313d192b9d871f1e543f8ac1209b0a9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ad6060180ef1fa5784a087be85d1f91.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1da9dcf6c319174c9ea2b1ceaed1649a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11a25178d007036b7fbde4ab793c98c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cfc6ee6f3b4da7817d30e1b9dc36d2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bff1301d5d66379471b648952aea6310.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/26e93d8fb77f5bd2c0fc690752dfd771.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4d7e9f86738335a22298559db41037a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ad6060180ef1fa5784a087be85d1f91.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1da9dcf6c319174c9ea2b1ceaed1649a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1da9dcf6c319174c9ea2b1ceaed1649a.png)
您最近一年使用:0次
2022-10-26更新
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179次组卷
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2卷引用:上海市进才中学2022-2023学年高一上学期10月月考数学试题
2 . 四个人做一道选项为
的选择题,四个同学对话如下:
赵:我选
;钱:我选
当中的一个;孙:我选
;李:我选
;
四个人每人选了一个选项,而且各不相同,其中只有一个人说谎,则说谎的人可能是谁?( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf38f43d820c85fc06020c81bb45c00f.png)
赵:我选
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/525523273b64758484e178d4359d4d59.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f015ed8e497b4394053ddd19683a98f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7909220d1db380634534190b662ee0a7.png)
四个人每人选了一个选项,而且各不相同,其中只有一个人说谎,则说谎的人可能是谁?( )
A.赵,钱 | B.钱,孙 | C.孙,李 | D.李,赵 |
您最近一年使用:0次
2022-05-28更新
|
373次组卷
|
4卷引用:上海市金山中学2022-2023学年高一上学期期末数学试题
3 . 对于问题“设实数
满足
,证明:
,
,
中至少有一个不超过
”.甲、乙、丙三个同学都用反证法来证明,他们的解题思路分别如下:
甲同学:假设对于满足
的任意实数
,
,
,
都大于
.
再找出一组满足
但与“
,
,
都大于
”矛盾的
,从而证明原命题.
乙同学:假设存在满足
的实数
,
,
,
都大于
.
再证明所有满足
的
均与“
,
,
都大于
”矛盾,从而证明原命题.
丙同学:假设存在满足
的实数
,
,
,
都大于
.
再证明所有满足
的
均与“
,
,
都大于
”矛盾,从而证明原命题.那么,下列正确的选项为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76f0649064a085fb74c997fb507a9b6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1f9223bc24df8d429d743692fff7c06.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a13880b9454c5942f164d934b1834783.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/176400fc97133ee3a7bba932544318ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb00b6918dfb251c1a63acdc07464b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d5989c84e320b504511f23eeb6e7357.png)
甲同学:假设对于满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1f9223bc24df8d429d743692fff7c06.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76f0649064a085fb74c997fb507a9b6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a13880b9454c5942f164d934b1834783.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/176400fc97133ee3a7bba932544318ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb00b6918dfb251c1a63acdc07464b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d5989c84e320b504511f23eeb6e7357.png)
再找出一组满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1f9223bc24df8d429d743692fff7c06.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a13880b9454c5942f164d934b1834783.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/176400fc97133ee3a7bba932544318ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb00b6918dfb251c1a63acdc07464b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d5989c84e320b504511f23eeb6e7357.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76f0649064a085fb74c997fb507a9b6d.png)
乙同学:假设存在满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1f9223bc24df8d429d743692fff7c06.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76f0649064a085fb74c997fb507a9b6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a13880b9454c5942f164d934b1834783.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/176400fc97133ee3a7bba932544318ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb00b6918dfb251c1a63acdc07464b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d5989c84e320b504511f23eeb6e7357.png)
再证明所有满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1f9223bc24df8d429d743692fff7c06.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76f0649064a085fb74c997fb507a9b6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a13880b9454c5942f164d934b1834783.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/176400fc97133ee3a7bba932544318ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb00b6918dfb251c1a63acdc07464b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d5989c84e320b504511f23eeb6e7357.png)
丙同学:假设存在满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9dad69e399b3b4f68b777f6678c7ced7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76f0649064a085fb74c997fb507a9b6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a13880b9454c5942f164d934b1834783.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/176400fc97133ee3a7bba932544318ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb00b6918dfb251c1a63acdc07464b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d5989c84e320b504511f23eeb6e7357.png)
再证明所有满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9dad69e399b3b4f68b777f6678c7ced7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76f0649064a085fb74c997fb507a9b6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a13880b9454c5942f164d934b1834783.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/176400fc97133ee3a7bba932544318ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb00b6918dfb251c1a63acdc07464b92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d5989c84e320b504511f23eeb6e7357.png)
A.只有甲同学的解题思路正确 | B.只有乙同学的解题思路正确 |
C.只有丙同学的解题思路正确 | D.有两位同学的解题思路都正确 |
您最近一年使用:0次
2022-10-14更新
|
111次组卷
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2卷引用:上海市浦东复旦附中分校2022-2023学年高一上学期10月月考数学试题