# All Questions

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### Every ordered field that has the least upper bound property is isomorphic to the real number system.

Okay, so here's a theorem from Rudin: "Every ordered field that has the least upper bound property is isomorphic to the real number system." Here's a definition: "Ordered fields are isomorphic if ...
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### Find first positive perfect square in polynomial time

I have a quadratic. for example $$1x^2+6884x+3297$$ Is it possible to find the first perfect square in the series in polynomial time where both x and y are whole positive integers. In the above ...
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### Mathematicians who didn't study mathematics in college or university

I would like to know mathematicians who were born after 1900 who didn't study mathematics in college or university. I posted a similar question recently but it was closed as opinion based. So I will ...
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### Divisors and non divisors

How do i prove: The sum over the numbers that don't share a divisor with the divisors of n, including n it self, will be n-1. Example $n=12$: The numbers that share a divior are $2;3;4;6;12$. ...
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### Automorphism group of a locally cyclic group

I am having difficulty proving that: The automorphism group of a locally cyclic group is commutative. Is there any easy way to prove it? Thanks.
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### $|(a,b)| = |\Bbb R|$ ? Cardinality of any open interval

I want to prove that any open interval $(a,b)$ has the same cardinality of the real numbers: $|(a,b)| = |\Bbb R|$. Do I have to find an function to prove it? Or is there a theorem to prove it ...
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