All Questions
Tagged with congruences diophantine-equations
7 questions
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When is $\phi(a^n+b^n+c^n)=0\mod n$?
A corollary Zsigmondy's Theorem leads to the following congruence (one can look to $(24)$),$\phi(a^n+b^n)=0\mod n$ whenever $a, b$ are coprime and $n \neq 2$ and $(a,b)\neq(1,1)$. (Here $\phi$ is the ...
user147204
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3
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Finding a solution for this system of two diophantine equations (depending on a parameter) [closed]
I propose the following problem (Maybe it has a trivial solution):
Let $n$ be a positive integer such that $$n\equiv1 \pmod 4.$$
Then the problem is to find a rational $x$ as a function of $n$ such ...
- 1,197
3
votes
1
answer
522
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Solvability of Diophantine equation using congruences where the variables are bounded?
In page 2 of Mordell "Diophantion equations" it is given a necessary condition for the solvability of a Diophantine equation:
Integer solutions of the inhomogeneous equation $f(x) = 0$ can exist only ...
- 841
7
votes
2
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780
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Some equalities involving prime powers
Let $p,a,b,x,y$ be positive integers where $p$ is an odd prime; $x$ and $y$ are odd; $p,x$ and $y$ are all coprime. I'm interested in finding examples of such numbers that satisfy this equation:
\...
- 11.2k
13
votes
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answer
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On cubic reciprocity for $x^3+y^3+z^3 = 996$?
I. The Diophantine equation,
$$x^3+y^3+z^3 = 3w^3\tag1$$
with $x\geq y \geq z$ and $w=1$ has only two known solutions, namely $1,1,1$ and $4,4,-5$. Are there larger ones? As Noam Elkies points out ...
- 12.6k
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600
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Systems of linear modular equations with unknowns in the moduli
I am interested in systems of linear modular equations, where the unknowns also appear in the moduli. The general form would be:
$A \vec{x}= \vec{b} \;\textrm{mod} \; (C \vec{x}+\vec{d})$
where A ...
- 940
11
votes
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A congruence conjecture regarding $(r-s)^4-1 \equiv 0\!\pmod{4r^2s}$
Is the following conjecture true?
Conjecture. If $r > s \ge 1$ are relatively prime integers such that
\begin{equation}
(r-s)^4-1 \equiv 0\!\pmod{4r^2s}, \tag{1}
\end{equation}
then $r-s = 1$ ...
- 1,055