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ThePortakal
  • Member for 8 years, 3 months
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78 votes
Accepted

Given $g(x)$ and $f(g(x))$, solve for $f(x)$.

38 votes

Most ambiguous and inconsistent phrases and notations in maths

8 votes

"Here's a cool problem": a collection of short questions with clever solutions

7 votes

Boundary of a bounded open set in $\mathbb{R}^2$

6 votes
Accepted

Find all numbers $n\in \{ 1,...,100 \}$ which have 5 unique divisors.

5 votes

Set intersection theory

5 votes

Why isn't the Cantor set a discrete topology?

5 votes

Given seven points inside a hexagon with side length $1$ prove that there exists two points with distance at most $1$

5 votes

Doesn't this prove that $n^2+1$ contains infinitely many primes?

4 votes
Accepted

Show that exists a continuous function in $E$ that is not bounded

4 votes
Accepted

How many of the numbers in $A=\{1!,2!,...,2015!\}$ are square numbers?

4 votes
Accepted

Prove that $\overline{A}=\overline{B}$ implies that, for $f:X\rightarrow Y$ continuous, $\overline{f(A)}=\overline{f(B)}$

4 votes
Accepted

$f(x) = \frac{2}{x}$ is not uniformly continuous on $(0,1]$

4 votes

Find $x$ such that $\frac{(1+ 2i)^2}{x+i}$ is purely imaginary

4 votes

What is the geometrical definition of the $\sec\theta$

4 votes

Convergence when the comparison test cannot be applied

4 votes

Proving that if $A$ is a closed set then $\bar{A} = A$

4 votes

An alternating series convergence

3 votes

How many real roots does the equation $e^x-x^2=0$ have?

3 votes
Accepted

How I Prove $\sup(A)^{\sup(B)}=\sup(A^B)$

3 votes
Accepted

Inverse image of compact is compact will map be closed

3 votes
Accepted

If $f(x) = x\log2,$ then find $f'(x)?$

3 votes
Accepted

Integrating $ e^{3x^2} $

3 votes
Accepted

Set with infinitely many limit points not contained in S

3 votes

Does continuity depend on the distance function?

3 votes

How to determine the sum of an infinite series that is neither arithmetic nor geometric?

3 votes

How does proof by contradiction work?

3 votes

Finite sum where every term is a square root

2 votes
Accepted

Find dx/dt with 3 given datapoints

2 votes
Accepted

If $\int_{1}^{\infty}f\left(x\right)dx$ converges absolutely then $\int_{1}^{\infty}f^{2}\left(x\right)dx$ converges?