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If $a, b$ and $c$ are positive integers with $a, b ≥ 2$, then equation (1.1) has at most one solution in positive integers $x$ and $y$ with $b^y ≥ 6000 c^{1/δ∗(a,b)}.$

I'm unclear about the above usage of the word 'with'; is this theorem saying

IF $b^y ≥ 6000 c^{1/δ∗(a,b)}$ THEN equation (1.1) has at most one solution

or

IF equation (1.1) has at most one solution THEN $b^y ≥ 6000 c^{1/δ∗(a,b)},$

or

is it an IFF statement?

ryang
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Nimish
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1 Answers1

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If $a, b$ and $c$ are positive integers with $a, b ≥ 2$, then equation (1.1) has at most one solution in positive integers $x$ and $y$ with $b^y ≥ 6000 c^{1/δ∗(a,b)}.$

In the above theorem, the two copies of with both have a logical 'and' sense and can be replaced with the phrase 'such that':

  • If $a,b$ and $c$ are positive integers such that neither $a$ nor $b$ is $1,$ then if $x$ and $y$ are positive integers such that $b^y ≥ 6000 c^{1/δ∗(a,b)},$ then equation (1.1) has at most one solution

  • $a,b$ and $c$ are positive integers and neither $a$ nor $b$ is $1\quad\implies$

    ($x$ and $y$ are positive integers and $b^y ≥ 6000 c^{1/δ∗(a,b)}$ $\implies$ equation (1.1) has at most one solution)

  • $a,b,c,x$ and $y$ are positive integers  and  neither $a$ nor $b$ is $1$  and  $b^y ≥ 6000 c^{1/δ∗(a,b)}\quad\quad\implies$ equation (1.1) has at most one solution.

is this theorem saying

IF $b^y ≥ 6000 c^{1/δ∗(a,b)}$ THEN

No. That implicit conditional (the second '⟹' in the second bullet) above is actually not due to the word with per se, because its condition is actually the entire chunk “in positive integers $x$ and $y$ with $b^y ≥ 6000 c^{1/δ∗(a,b)}\,$”.

In this answer, I explain why the words with and where are frequently ambiguous in logic translations.

ryang
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