User Adriano - Mathematics Stack Exchange

18 votes

3 answers

5k views

Change of Variables in Limits (Part 1)

asked Jul 31, 2013 at 0:22

11 votes

3 answers

54k views

Necessary and sufficient conditions for differentiability.

asked May 9, 2013 at 20:47

4 votes

2 answers

402 views

Can the ceiling function be used to prove the Archimedean property?

asked Jun 28, 2013 at 9:37

3 votes

1 answer

158 views

Show that a function with a finite domain and a finite codomain is surjective if and only if it is injective.

asked May 10, 2013 at 4:37

3 votes

1 answer

289 views

Find the flaw in my proof that $z^2 =1$ has more than $2$ distinct solutions.

asked May 23, 2013 at 6:08

3 votes

1 answer

925 views

Using the definition of big-oh notation, show that for any $k,\gamma>1$, $n^k=O(\gamma^n)$.

asked Jul 21, 2013 at 0:27

3 votes

1 answer

234 views

Does $\neg(x > y)$ imply that $y \geq x$?

asked Jan 5, 2014 at 22:05

2 votes

2 answers

157 views

Any two points inside a circle are within a diameter of each other.

asked Aug 29, 2014 at 17:04

2 votes

2 answers

92 views

Are there $a,b,c,d \in \mathbb N$ such that $\frac{a + b}{a + b + c + d} < \frac{a}{a + c} < \frac{b}{b + d}$?

asked Sep 28, 2015 at 2:17

2 votes

1 answer

1k views

Does closure under the union and concatenation operations imply closure under the star operation?

asked Sep 6, 2013 at 9:51

1 vote

1 answer

293 views

If $p$ is irreducible and $p \not \mid a$, then $\text{gcd}(p,a)=\pm 1$.

asked Aug 13, 2013 at 22:30

0 votes

3 answers

197 views

If $G$ is disconnected and the vertices $x,y$ are adjacent in $G$, then there is a vertex that isn't adjacent to $x$ and isn't adjacent to $y$.

asked Jul 4, 2013 at 7:24

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12 Questions

Change of Variables in Limits (Part 1)

Necessary and sufficient conditions for differentiability.

Can the ceiling function be used to prove the Archimedean property?

Show that a function with a finite domain and a finite codomain is surjective if and only if it is injective.

Find the flaw in my proof that $z^2 =1$ has more than $2$ distinct solutions.

Using the definition of big-oh notation, show that for any $k,\gamma>1$, $n^k=O(\gamma^n)$.

Does $\neg(x > y)$ imply that $y \geq x$?

Any two points inside a circle are within a diameter of each other.

Are there $a,b,c,d \in \mathbb N$ such that $\frac{a + b}{a + b + c + d} < \frac{a}{a + c} < \frac{b}{b + d}$?

Does closure under the union and concatenation operations imply closure under the star operation?

If $p$ is irreducible and $p \not \mid a$, then $\text{gcd}(p,a)=\pm 1$.

If $G$ is disconnected and the vertices $x,y$ are adjacent in $G$, then there is a vertex that isn't adjacent to $x$ and isn't adjacent to $y$.