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Astyx's user avatar
Astyx's user avatar
Astyx
  • Member for 7 years, 8 months
  • Last seen this week
33 votes

What is the total sum of the cardinalities of all subsets of a set?

11 votes

A wrong mathematical induction

10 votes
Accepted

How to find sum of $n^{3}/n!$, when $n$ goes from 0 to infinity?

7 votes
Accepted

How can I solve this limit involving $1/\sqrt{n^2+2n}$?

5 votes

How to prove that $e^x=x$ has no real solution?

5 votes
Accepted

Example of prime decomposition using Dedekind theorem in $\Bbb{Q}(\sqrt{3})$

4 votes

How to find an orthonormal basis for $ P_{2}(\mathbb R)$ equipped with the inner product $\langle f,g\rangle =f(-1)g(-1)+f(0)g(0)+f(1)g(1)$?

4 votes
Accepted

How to prove $\small\begin {cases} U \subseteq V \\ V \subseteq U + W\end{cases} \Rightarrow V \subseteq W$?

4 votes
Accepted

For what values of $\theta$ does $\sum_{1}^{\infty} \frac{e^{i n\theta}}{n}$ Converge?

4 votes
Accepted

Equivalence of two definitions for very ampleness

4 votes
Accepted

$f(f(x - y)) = f(x) f(y) - f(x) + f(y) - xy$

4 votes
Accepted

Determine if algorithm is infinite for the pair of positive integers $(n,m)$

4 votes

Nontrivial rational solution of $x^3-3x^2+3x+1=y^2$

3 votes
Accepted

Euler product formula

3 votes
Accepted

Prove $a^{2}(1+b^{2})+b^{2}(1+c^{2})+c^{2}(1+a^2)\geq 6abc$

3 votes
Accepted

sum of all the digits of the integers from one integer to another

3 votes

Vector space of $m\times n$ matrix $\Bbb R^{m\times n}$ vs vector space of a vector of size $mn$ $\Bbb R^{mn}$?

3 votes

Show that $f(x) = \cos(x/4)e^{-x/4}$ has a fixed point in $[0,1]$. Show that it has only one fixed point in total. Is it a stable fixed point?

3 votes
Accepted

Find all values of $ r $ such that $ a_n = r^n $ for $ n \in \mathbb{Z}_{\ge2} $ in a recurrence relation

3 votes
Accepted

Condition for special equivalence relation

3 votes
Accepted

3 equations with 4 unknowns and information about the unknowns' types

3 votes

Transitive property of linear dependence

3 votes

How did $DT^{-1}(x,y)=(DT(x,y))^{-1}$ followed from the chain rule?

3 votes

Determine $\int^{\infty}_1 \frac1{x^2+x} \mathrm d x$

3 votes

Why doesn't multiplying square roots of imaginary numbers follow $\sqrt{a} \times \sqrt{b} = \sqrt{ab}$?

3 votes
Accepted

How can I prove that $X+Y$ is a Poisson process with parameter $\lambda_X+\lambda_Y$?

3 votes

$f(x^2)=(f(x))^2=f(f(x))$, $\forall x\in\mathbb R$.

2 votes
Accepted

Proof $\sum_{k=1}^{p-1}\left\lfloor\dfrac{km}{p}\right\rfloor=\dfrac{(m-1)(p-1)}{2}$ with $m$ and $p$ co-prime numbers

2 votes
Accepted

If $H$ and $K$ are finite supgroups of a group $G$, then $|HK| = \frac{|H||K|}{|H\cap K|}$

2 votes
Accepted

Derivative of $trace(|A|)$ with respect to $A$

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