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1h
comment Irreducibility of a polynomial
$f(1/x)$ doesn't look like a polynomial, because it isn't a polynomial (if the degree of $f$ exceeds zero). But $x^nf(1/x)$ is a polynomial.
10h
revised Composition of functions, injectivity, and surjectivity
edited tags, more informative title
10h
comment Can such an “orthogonal” matrix exist?
You can post that as an answer, Oria. It is encouraged to post answers to your own questions, if a discussion has shown you how to do them.
13h
awarded  Good Answer
1d
comment how many spheres can all touch a single one?
While you are thinking about the more general problem, maybe you could post an answer to the particular problem in the question, based on what you have learned by following the links. Oh, and if you want to be sure I see a comment addressed to me, you have to write @Gerry in it somewhere.
1d
comment Can Stirling's approximation be used to obtain lower and upper bound for $\pi(x)$?
You may find mathoverflow.net/questions/42393/… interesting.
2d
comment how many spheres can all touch a single one?
So, Thomas, have you followed the links?
2d
comment Fractional part of $n\alpha$ is equidistributed
@i70, yes, I think what I had i mind was the set of linear combinations of functions of the form $e^{2\pi inx}$, $n$ running through the integers.
2d
comment Something related to carmichael numbers.
And how well is that working for you?
2d
comment Is every axiom in the definition of a vector space necessary?
See previous discussions, e.g., math.stackexchange.com/questions/920763/…
2d
comment Trivial zeroes of Zeta are simple
Rudely simulposted to MO, without notice to either site. mathoverflow.net/questions/215840/…
2d
comment Rotating groups of people
I'm voting to close this question as off-topic because OP has abandoned it.
2d
comment Let A and B be two row equivalent matrices. Show that the columns of A and B have the same dependence relationships
I'm voting to close this question as off-topic because OP has abandoned it.
2d
comment Geometry - points on a sphere
@don, what about projecting a regular solid onto a sphere – doesn't that count as tiling a sphere with equilateral triangles, with squares, and with regular pentagons?
Aug
28
comment Proofs of trivial zeros of zeta function?
But see the discussion at mathoverflow.net/questions/215840/… for another point of view.
Aug
28
comment Find $\operatorname{min}(\omega\sqrt{2},\mathbb{Q})$
I take it your notation means the minimal polynomial for that number over the rationals. Well, try raising the number to the sixth power. That should get you started.
Aug
28
revised An example to prove that all cosets do not form a group
typo in title
Aug
28
comment Irreducibility of a polynomial
$x^nf(1/x)$ vs. $f(x)$.
Aug
28
comment how many spheres can all touch a single one?
Very famous problem. Newton and Gregory argued about it – Newton said, 12, Gregory, 13. See plus.maths.org/content/newton-and-kissing-problem
Aug
28
comment $n!$ is never a perfect square if $n\geq2$. Is there a proof of this that doesn't use Chebyshev's theorem?
Also, answered 6 times, 5 of them deleted (and the 6th is currently at $-4$).