1 . 若平面点集M满足:任意点(x,y)∈M,存在t∈(0,+∞),都有(tx,ty)∈M,则称该点集M是“t阶聚合”点集.现有四个命题:
①若M={(x,y)|y=2x},则存在正数t,使得M是“t阶聚合”点集;
②若M={(x,y)|y=x2},则M是“
阶聚合”点集;
③若M={(x,y)|x2+y2+2x+4y=0},则M是“2阶聚合”点集;
④若M={(x,y)|x2+y2≤1}是“t阶聚合”点集,则t的取值范围是(0,1].
其中正确命题的序号为
①若M={(x,y)|y=2x},则存在正数t,使得M是“t阶聚合”点集;
②若M={(x,y)|y=x2},则M是“
![](https://img.xkw.com/dksih/QBM/2016/3/18/1572546403147776/1572546408783872/STEM/343a394834424e23bf4d72fde23c2d7b.png)
③若M={(x,y)|x2+y2+2x+4y=0},则M是“2阶聚合”点集;
④若M={(x,y)|x2+y2≤1}是“t阶聚合”点集,则t的取值范围是(0,1].
其中正确命题的序号为
A.①② | B.②③ | C.①④ | D.③④ |
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2 . 已知集合
对于
,
,定义
与
的差为
,定义
与
之间的距离为
.对于
,则下列结论中一定成立的是
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A.![]() | B.![]() |
C.![]() | D.![]() |
您最近一年使用:0次
3 . 已知集合
对于
,
,定义
与
的差为
,定义
与
之间的距离为
.对于
,则下列结论中一定成立的是
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a28f20ac38afe51a1e34594a07fd63d0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/269b6323a15f70e67290637cb94ebf9b.png)
![](https://img.xkw.com/dksih/QBM/2015/3/26/1572037567160320/1572037572231168/STEM/2f96a384b0884eaa8f288a8d363282ef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d4d68a2c23633de5e32b8d8d69fa8f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ca0edf97ed3ac5ddb038d4341b090b6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b2093520791e9de28c6cffef30746803.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
您最近一年使用:0次