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Jan
13
reviewed Close power e irrational number
Jan
13
reviewed Close Maths problem on distance
Jan
13
reviewed Close Prove the following inequality without using differentiation
Jan
13
reviewed Leave Open If such $1+4\sin{10^\circ}=a+b\sin{c^\circ}$ How find this integer $a,b$
Jan
13
comment Summation with Binomial Coefficients, $\sum (-1)^k \binom{m_1}{k} \binom{m_2}{k} $
related: $\sum(-1)^k\binom mk^2$
Jan
13
revised Summation with Binomial Coefficients, $\sum (-1)^k \binom{m_1}{k} \binom{m_2}{k} $
more descriptive title
Jan
12
comment Groups with no nontrivial topology
(Re: «I am quite interested in how the problem changes if G is infinite or finite.») That's easy to answer: changes from completely trivial (finite) to very hard problem that stayed open for almost 40 years (infinite).
Jan
12
comment Groups with no nontrivial topology
@ MO: mathoverflow.net/questions/165783/…
Jan
12
reviewed Close Find a polynomial of degree 3 with rational coefficients, given remainders mod two quadratics
Jan
12
reviewed Close Find all invariant subspace of $A$
Jan
12
reviewed Close limit of the function $x \to 1$
Jan
12
reviewed Close Convention for dummy variables
Jan
12
reviewed Close How to find $R^2$ given $S$ and $R$.
Jan
12
reviewed Close Optimization problem of two variable
Jan
12
reviewed Close Show that function $f: A \to B$ is surjective when there is an implication: $g \circ f = h\circ f \to g=h$
Jan
12
reviewed Close $\lim\limits_{x\to\infty} \frac{\sqrt{(4x +3) +2\sqrt{1+ x}}}{\sqrt x}$ without L'Hôpital's rule
Jan
12
reviewed Leave Closed Open sets in locally compact spaces
Jan
12
reviewed Looks OK Limit of density points is a density point?
Jan
12
reviewed Close Is $\bigl(\sum {{x^n}\over{n!}} \bigr) \bigl(\sum {{y^n}\over{n!}} \bigr) = \bigl(\sum {{(x+y)^n}\over{n!}}\bigr)$ generalizable for series?
Jan
12
reviewed Close How are contest problems designed?