Le Anh Dung

# 266 Questions

2
10
1
371
views

1
8
2
116
views

1
6
1
148
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1
5
1
126
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1
5
2
335
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5
1
95
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1
4
2
88
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1
4
1
46
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4
1
55
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4
0
115
views

### If $A$ and $B$ are countable, then $A\times B$ is countable

Sep 12 at 17:06 Le Anh Dung 1,485

4
2
111
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4
1
158
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1
4
0
197
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### Is this a mistake in the proof of Hall's Marriage Theorem from https://proofwiki.org?

Jun 10 '18 at 17:12 Le Anh Dung 1,485
1
4
2
130
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3
2
36
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3
1
67
views

3
2
59
views

3
0
68
views

### The smallest subfield of a complete ordered field is dense in itself

Jan 22 at 13:18 Le Anh Dung 1,485
1
3
2
79
views

3
0
40
views

### There is a unique isomorphism from $\langle \Bbb Q,<,+,\cdot,0,1 \rangle$ to an ordered field

Jan 9 at 2:57 Le Anh Dung 1,485

3
0
50
views

### Prove that $\forall x \in \Bbb R^+:x+0=x\cdot 1=x$

Jan 4 at 4:29 Le Anh Dung 1,485

3
1
90
views

3
0
38
views

### For every natural number $a \ge 2$, every natural number $m$ can be written in base $a$

Nov 20 at 11:14 Le Anh Dung 1,485

3
1
76
views

3
0
25
views

### Suppose that $X$ is a set of ordinals. Then $\bigcup X$ is transitive

Oct 14 at 13:37 Le Anh Dung 1,485

3
1
43
views

3
3
75
views

4
3
1
817
views

3
0
69
views

### Suppose that $Z \subseteq Y \subseteq X$ and that $f:X \to Z$ is bijective, then there exists a bijection $g : X \to Y$

Apr 14 '18 at 15:56 Le Anh Dung 1,485
1
3