1 . 某校数学兴趣小组有14位同学,他们组成了n个不同的课题组.每个课题组有6位同学,每位同学至少参加2个课题组,且任意两个课题组至多有2位共同的同学,求n的最大值.
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2 . 如图,
、
分别是△ABC、△ACD的重心,
的外接圆与直线BD相交于点P,且
,求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc71c35d851ff74646c728756b24efb2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/951d73cefe3fed1c5e70210ce71ae2fb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5035afd29380c8912a02ac79a7db19b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7a69a73f2044f45086374c2e068b548.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3269cf61861183004455d640aac8ccf0.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/25/ada6f890-0c6f-474f-a6a8-d92f18e4566a.jpg?resizew=193)
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3 . 已知
,
,…,
是集合
的n个非空子集,如果对于任意的i,
,均有
,则n的最大值为___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f9721059d158853671eaf19e39769b13.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cd8db4b168ddbcba90ac9b31d36a0432.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d3cfeacc29e6a61c5b3b4e439c0a91df.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/64e11e77f3276edde5c0a9f2057beb44.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9a42daf2970136f21f3e5b3b2f96fe44.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac30abcc83eecff9e2cb8dabc1d10ac8.png)
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