Do two pairs of distinct natural numbers exist such that AGM(A,B) equal to AGM(C,D)?












0












$begingroup$


Here AGM is arithmetic-geometric mean.



Are there natural numbers A,B,C,D such that $1leq A<C<D<B$ and arithmetic-geometric mean AGM(A,B)=AGM(C,D) ?



In other words, is AGM a homomorphism of an unordered pair of natural numbers on a set of real numbers?










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$endgroup$












  • $begingroup$
    Isn't $A<AGM(A,B)<B?$ How could this be true?
    $endgroup$
    – saulspatz
    Jan 13 at 15:46












  • $begingroup$
    The questions in your title and body are different. In particular, the answer to the question in the body is trivially no: $AGM(A,B) leq B < C leq AGM(C,D)$, but the question in the title does not suffer from this problem. In particular, for any such example, we must have either $A < C < D < B$, or one of the obvious permutations of that.
    $endgroup$
    – user3482749
    Jan 13 at 15:48










  • $begingroup$
    Typo. Corrected
    $endgroup$
    – Stepan
    Jan 13 at 15:49
















0












$begingroup$


Here AGM is arithmetic-geometric mean.



Are there natural numbers A,B,C,D such that $1leq A<C<D<B$ and arithmetic-geometric mean AGM(A,B)=AGM(C,D) ?



In other words, is AGM a homomorphism of an unordered pair of natural numbers on a set of real numbers?










share|cite|improve this question











$endgroup$












  • $begingroup$
    Isn't $A<AGM(A,B)<B?$ How could this be true?
    $endgroup$
    – saulspatz
    Jan 13 at 15:46












  • $begingroup$
    The questions in your title and body are different. In particular, the answer to the question in the body is trivially no: $AGM(A,B) leq B < C leq AGM(C,D)$, but the question in the title does not suffer from this problem. In particular, for any such example, we must have either $A < C < D < B$, or one of the obvious permutations of that.
    $endgroup$
    – user3482749
    Jan 13 at 15:48










  • $begingroup$
    Typo. Corrected
    $endgroup$
    – Stepan
    Jan 13 at 15:49














0












0








0





$begingroup$


Here AGM is arithmetic-geometric mean.



Are there natural numbers A,B,C,D such that $1leq A<C<D<B$ and arithmetic-geometric mean AGM(A,B)=AGM(C,D) ?



In other words, is AGM a homomorphism of an unordered pair of natural numbers on a set of real numbers?










share|cite|improve this question











$endgroup$




Here AGM is arithmetic-geometric mean.



Are there natural numbers A,B,C,D such that $1leq A<C<D<B$ and arithmetic-geometric mean AGM(A,B)=AGM(C,D) ?



In other words, is AGM a homomorphism of an unordered pair of natural numbers on a set of real numbers?







means natural-numbers






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 13 at 15:49







Stepan

















asked Jan 13 at 15:44









StepanStepan

468312




468312












  • $begingroup$
    Isn't $A<AGM(A,B)<B?$ How could this be true?
    $endgroup$
    – saulspatz
    Jan 13 at 15:46












  • $begingroup$
    The questions in your title and body are different. In particular, the answer to the question in the body is trivially no: $AGM(A,B) leq B < C leq AGM(C,D)$, but the question in the title does not suffer from this problem. In particular, for any such example, we must have either $A < C < D < B$, or one of the obvious permutations of that.
    $endgroup$
    – user3482749
    Jan 13 at 15:48










  • $begingroup$
    Typo. Corrected
    $endgroup$
    – Stepan
    Jan 13 at 15:49


















  • $begingroup$
    Isn't $A<AGM(A,B)<B?$ How could this be true?
    $endgroup$
    – saulspatz
    Jan 13 at 15:46












  • $begingroup$
    The questions in your title and body are different. In particular, the answer to the question in the body is trivially no: $AGM(A,B) leq B < C leq AGM(C,D)$, but the question in the title does not suffer from this problem. In particular, for any such example, we must have either $A < C < D < B$, or one of the obvious permutations of that.
    $endgroup$
    – user3482749
    Jan 13 at 15:48










  • $begingroup$
    Typo. Corrected
    $endgroup$
    – Stepan
    Jan 13 at 15:49
















$begingroup$
Isn't $A<AGM(A,B)<B?$ How could this be true?
$endgroup$
– saulspatz
Jan 13 at 15:46






$begingroup$
Isn't $A<AGM(A,B)<B?$ How could this be true?
$endgroup$
– saulspatz
Jan 13 at 15:46














$begingroup$
The questions in your title and body are different. In particular, the answer to the question in the body is trivially no: $AGM(A,B) leq B < C leq AGM(C,D)$, but the question in the title does not suffer from this problem. In particular, for any such example, we must have either $A < C < D < B$, or one of the obvious permutations of that.
$endgroup$
– user3482749
Jan 13 at 15:48




$begingroup$
The questions in your title and body are different. In particular, the answer to the question in the body is trivially no: $AGM(A,B) leq B < C leq AGM(C,D)$, but the question in the title does not suffer from this problem. In particular, for any such example, we must have either $A < C < D < B$, or one of the obvious permutations of that.
$endgroup$
– user3482749
Jan 13 at 15:48












$begingroup$
Typo. Corrected
$endgroup$
– Stepan
Jan 13 at 15:49




$begingroup$
Typo. Corrected
$endgroup$
– Stepan
Jan 13 at 15:49










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