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Sorombo
  • Member for 8 years, 6 months
  • Last seen more than 1 year ago
  • Rio de Janeiro, Brazil
6 votes
Accepted

$f$-related vector field

6 votes

prove a function $f(x,y) = \max(x,y)$ is continuous

3 votes

$\sum_{1\le k\le n,~k\mathrm{~odd}}k\binom{n}{k}=n\cdot2^{n-2}$ for $n>1$

3 votes

If $A$ is a prime ideal on $R\times S$, then $A = P \times S$, where P is a prime ideal on R or $A = R\times Q$, where $Q$ is a prime ideal on $S$.

3 votes

Cyclic subgroup of finite index in $\text{PSL}_2(\mathbb{Z})$

2 votes
Accepted

Prove that $f(x) = 2x^{2}-3$ is continuous in all of $\mathbb{R}$

2 votes

Proving $x^4+2$ cannot be factored into $2$ degree polynomials

2 votes
Accepted

How to show that the measure of $\cap_n E_n $ is not $0$?

1 vote

Prove that if $n$ is an odd integer, then $n^2-1$ is divisible by $8$.

1 vote

de Rham cohomology of $\mathbb R^2 \setminus \mathbb Z^2 $

1 vote
Accepted

$2$-form $\mu$ is non-degenerate $\Leftrightarrow \mu\wedge...\wedge \mu\neq 0$

1 vote

Combinatorial proof using Pascal's identity

1 vote

$X$ complete. If $M \subset X$ closed then $(M,d)$ is complete.

1 vote
Accepted

$N|K$ normal $\Rightarrow F \in K[X]$ factors into $F=Q_1\cdots Q_r$ with $\text{deg}(Q_1)=\dots=\text{deg}(Q_r)$

1 vote

Prove T(n)= T(n-2)+k is O(n) for all n >1

0 votes

Nice proof of a polynomial root $x \in [0, 1]$

0 votes

Homomorphism or not?