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Top Questions
86
votes
What my dog really hears
code-golf
string
substitution
asked May 9, 2017 at 8:07
codegolf.stackexchange.com
46
votes
How can "[" be an operator in the PHP language specification?
php
specifications
asked Jan 9, 2016 at 14:42
stackoverflow.com
38
votes
A circle in the plane contains at most four lattice points?
euclidean-geometry
asked Jul 30, 2015 at 20:55
math.stackexchange.com
33
votes
Smallest order for finite group that needs many elements to generate it
group-theory
finite-groups
asked Nov 2, 2011 at 13:10
math.stackexchange.com
29
votes
Divisibility property for sequence $a_{n+2}=-2(n-1)(n+3)a_n-(2n+3)a_{n+1}$
sequences-and-series
modular-arithmetic
recurrence-relations
asked Apr 8, 2018 at 16:16
math.stackexchange.com
23
votes
Why is $(\sqrt{2}+\sqrt{3})^{2008}$ so close to an integer?
number-theory
algebraic-number-theory
approximation-theory
asked Jun 9, 2014 at 19:41
math.stackexchange.com
22
votes
Comparing countable models of ZFC
logic
set-theory
model-theory
asked Sep 13, 2011 at 4:35
math.stackexchange.com
21
votes
Are there statements that are undecidable but not provably undecidable
logic
set-theory
decidability
asked Sep 17, 2011 at 9:12
math.stackexchange.com
19
votes
Is $SO_n({\mathbb R})$ a divisible group?
linear-algebra
group-theory
lie-groups
divisible-groups
asked Dec 19, 2013 at 6:23
math.stackexchange.com
18
votes
Square root of positive definite nonsymmetric matrix
linear-algebra
matrices
asked Feb 10, 2014 at 7:24
math.stackexchange.com
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Top Answers
32
How to prove that minimum of two exponential random variables is another exponential random variable?
math.stackexchange.com
32
Is it possible for an irreducible polynomial with rational coefficients to have three zeros in an arithmetic progression?
math.stackexchange.com
30
Interesting Olympiad Style Problem about Invariance
math.stackexchange.com
25
Does there exist rational $a,b,c$, such that $\sqrt[3]{1}+\sqrt[3]{2}+\sqrt[3]{4}=\sqrt[3]{a}+\sqrt[3]{b}+\sqrt[3]{c}$
math.stackexchange.com
22
Galois group of a biquadratic quartic
math.stackexchange.com
20
Let $a_{i} \in\mathbb{R}$ ($i=1,2,\dots,n$), and $f(x)=\sum_{i=0}^{n}a_{i}x^i$ such that if $|x|\leqslant 1$, then $|f(x)|\leqslant 1$. Prove that:
math.stackexchange.com
18
Prove:$A B$ and $B A$ has the same characteristic polynomial.
math.stackexchange.com
17
Example of two dependent random variables that satisfy $E[f(X)f(Y)]=Ef(X)Ef(Y)$ for every $f$
math.stackexchange.com
16
convergence in probability induced by a metric
math.stackexchange.com
15
Prove that symplectic Lie algebras, $\mathfrak{sp}(n)$, are simple
math.stackexchange.com
15
Prove that $\phi(n) \geq \sqrt{n}/2$
math.stackexchange.com
15
Show that $P_i$ and $\sum_i P_i$ being idempotent implies $P_i P_j=\delta_{ij}$
math.stackexchange.com
15
Prove that $2^n-3$ is squarefree
math.stackexchange.com
14
$f(x)$ with real co-efficient and degree 2011 there is a real number $b$ such that $f(b)=f'(b)$
math.stackexchange.com
13
How to represent Fermat number $F_n$ as a sum of three squares?
math.stackexchange.com
13
Integers which are the sum of non-zero squares
math.stackexchange.com
13
what is the sum of this?$\frac12+ \frac13+\frac14+\frac15+\frac16 +\dots\frac{1}{2012}+\frac{1}{2013} $
math.stackexchange.com
12
When is a sum of consecutive squares equal to a square?
math.stackexchange.com
11
Understanding the proof of Schur-Weyl Duality
math.stackexchange.com
11
How find this determinant $\det(\cos^4{(i-j)})_{n\times n}$
math.stackexchange.com
11
Dual of a rational convex polyhedral cone
math.stackexchange.com
11
Integers expressible in the form $x^2 + 3y^2$
math.stackexchange.com
11
Algebra Iranian Olympiad Problem
math.stackexchange.com
11
Given $P(x)=x^{4}-4x^{3}+12x^{2}-24x+24,$ then $P(x)=|P(x)|$ for all real $x$
math.stackexchange.com
11
How does (21) factor into prime ideals in the ring $\mathbb{Z}[\sqrt{-5}]$?
math.stackexchange.com
10
How to find the eigenvalues and Jordan canonical form of this matrix
math.stackexchange.com
10
Find the value of $a+b+c$
math.stackexchange.com
10
Showing that $\mathbb{Q}(\zeta_p, \sqrt[p]{\ell}) = \mathbb{Q}(\zeta_p + \sqrt[p]{\ell})$ for $p,\ell$ primes.
math.stackexchange.com
10
Find rank of the matrix $a_{ij}=(i-j)^2$, $i,j=1,\dots, n$
math.stackexchange.com
10
Prove $f(x) = 0$ for all $x \in [0, \infty)$ when $|f'(x)| \leq |f(x)|$
math.stackexchange.com
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