User Wolfram

17 votes

Why does one have to check if axioms are true?

answered Feb 1, 2017 at 20:59

15 votes

Prove that $\sqrt{2}+\sqrt{3}+\sqrt{5}$ is irrational. Generalise this.

answered Feb 2, 2017 at 15:17

5 votes

Mathematical chessboard question complex

answered Feb 1, 2017 at 19:57

5 votes

Accepted

On the four and five color theorems

answered Feb 5, 2017 at 12:37

5 votes

Accepted

How to round numbers fairly

answered Feb 9, 2017 at 23:43

5 votes

Accepted

Prove/Disprove: Find $a\in S_4$ that is not a power of $b$ such that $ab=ba$ while $b=(123)$

answered Jan 28, 2017 at 18:13

4 votes

Accepted

Invertibility of operator given surjectivity of adjoint

answered Jan 29, 2017 at 19:12

4 votes

If $A\cong B$ and $C\cong D$ how can I prove that $A/C\cong B/D$?

answered Feb 4, 2017 at 22:21

3 votes

Chess rook tour of 64 moves

answered Feb 7, 2017 at 22:15

3 votes

Consistency of ZFC and proof by contradiction

answered Feb 9, 2017 at 11:49

3 votes

A Diophantine equation involving factorial

answered Feb 2, 2017 at 12:25

3 votes

Accepted

Why does using the identity $e^x=1/e^{-x}$ work better in evaluating negative numbers in the finite taylor series expansion of $e^(x)$

answered Jan 29, 2017 at 21:44

3 votes

Two inequalities involving the rearrangement inequality

answered Feb 2, 2017 at 19:53

3 votes

How many numbers smaller than $10^6$ contain exactly three '$9$'s and have an odd sum of digits?

answered Feb 4, 2017 at 21:11

3 votes

Accepted

Proof involving a maximal subgroup

answered Jan 31, 2017 at 16:23

2 votes

Showing a number $n$ is prime if $(n-2)! \equiv 1 \pmod n$

answered Feb 1, 2017 at 21:14

2 votes

What do I miss? $\ln(x^2 -4) = \ln(1-4x)$, $x \neq 1$

answered Feb 2, 2017 at 19:22

2 votes

Prove that the complement of a point in a metric space is open

answered Feb 1, 2017 at 20:24

2 votes

If you get the remainder of two numbers, add the remainder to the larger number, and repeat the process, will there eventually be no remainder?

answered Jan 29, 2017 at 20:05

2 votes

limit superior of $\cos(x^2)-\cos[(x+1)^2]$ as $x \rightarrow \infty$

answered Jan 29, 2017 at 12:44

2 votes

Accepted

Deriving summation formulas

answered Jan 29, 2017 at 13:17

2 votes

There are any closed subspaces for $\ell^{2}$ such that $H_{s} \subset H_{t}$ such that $s < t$ for $0 \leq s, t \leq 1$?

answered Jan 28, 2017 at 19:28

2 votes

Equation for a smooth step function

answered Dec 10, 2016 at 22:00

2 votes

Probability of double matchings

answered Jan 29, 2017 at 10:47

2 votes

Accepted

Number of elements of order 2

answered Feb 11, 2017 at 10:48

2 votes

Conditions required to yield exactly one solution in Bertrand's Paradox

answered Feb 13, 2017 at 17:10

2 votes

Accepted

Prove that there are minimum of 90 matches played

answered Mar 3, 2017 at 18:25

2 votes

Accepted

Find $n_i$ integers such that $\sum_i n_i$ is constant and $\sum_i (1/n_i)$ is minimum

answered Feb 11, 2017 at 20:43

2 votes

Accepted

A question regarding a proof for a normal subgroup

answered Feb 9, 2017 at 11:34

2 votes

Trouble with Open Set Basis in Zariski

answered Feb 10, 2017 at 19:34

Stack Exchange Network

57 Answers

Why does one have to check if axioms are true?

Prove that $\sqrt{2}+\sqrt{3}+\sqrt{5}$ is irrational. Generalise this.

Mathematical chessboard question complex

On the four and five color theorems

How to round numbers fairly

Prove/Disprove: Find $a\in S_4$ that is not a power of $b$ such that $ab=ba$ while $b=(123)$

Invertibility of operator given surjectivity of adjoint

If $A\cong B$ and $C\cong D$ how can I prove that $A/C\cong B/D$?

Chess rook tour of 64 moves

Consistency of ZFC and proof by contradiction

A Diophantine equation involving factorial

Why does using the identity $e^x=1/e^{-x}$ work better in evaluating negative numbers in the finite taylor series expansion of $e^(x)$

Two inequalities involving the rearrangement inequality

How many numbers smaller than $10^6$ contain exactly three '$9$'s and have an odd sum of digits?

Proof involving a maximal subgroup

Showing a number $n$ is prime if $(n-2)! \equiv 1 \pmod n$

What do I miss? $\ln(x^2 -4) = \ln(1-4x)$, $x \neq 1$

Prove that the complement of a point in a metric space is open

If you get the remainder of two numbers, add the remainder to the larger number, and repeat the process, will there eventually be no remainder?

limit superior of $\cos(x^2)-\cos[(x+1)^2]$ as $x \rightarrow \infty$

Deriving summation formulas

There are any closed subspaces for $\ell^{2}$ such that $H_{s} \subset H_{t}$ such that $s < t$ for $0 \leq s, t \leq 1$?

Equation for a smooth step function

Probability of double matchings

Number of elements of order 2

Conditions required to yield exactly one solution in Bertrand's Paradox

Prove that there are minimum of 90 matches played

Find $n_i$ integers such that $\sum_i n_i$ is constant and $\sum_i (1/n_i)$ is minimum

A question regarding a proof for a normal subgroup

Trouble with Open Set Basis in Zariski