Can a Basis Be Proven with Divisibility?

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    Arithmetic Basis
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Homework Help Overview

The discussion revolves around proving a property related to divisibility and its implications for establishing a basis in a mathematical context. The original poster is attempting to demonstrate that if a certain condition involving divisibility holds, then it leads to conclusions about the divisibility of individual terms.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster explores the implications of divisibility, questioning the validity of their assertion regarding k dividing both a and b based on given conditions. Participants raise counterexamples and considerations regarding the nature of k, particularly when it is prime or equal to specific values.

Discussion Status

The discussion is active, with participants providing insights and questioning assumptions. Some guidance has been offered regarding the implications of k being prime and the specific case of k equal to 2, indicating a productive exploration of the topic.

Contextual Notes

Participants are considering various scenarios, including the parity of a and b, and the implications of k being prime or equal to certain values. There is an acknowledgment of the complexity surrounding the assumptions made in the original statement.

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Homework Statement


Hi everyone.
I'm studying a problem and I need to prove that I have a basis. I tryed a proof and to achieve it I need to show that :

if k divides a*b and also divides a2 +2*b2 Then k divides both a and b.


Homework Equations



I'm not sure what I'm asserting is true but if it was, then it would be great for me ( cause my proof would be finished).
I first thought that if k divided a sum then it divided every term of that sum but I understood it was wrong (the other way is correct).

I'm taking any idea!
 
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No, what if a = b and k = a2 in general?
 


Tedjn said:
No, what if a = b and k = a2 in general?

That's right indeed. But what if k is prime??
 


If k = 2, then no. Why? If k > 2 is prime, then yes. Why? Use the property that if p is prime and divides ab, then it divides a or b.
 


I can see if k>2, thank you, but why is it wrong if k=2 ?
 


Let a be even and b be odd.
 

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