Is 3 a Common Divisor for p and q When 3p² = q²?

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The discussion centers on proving that 3 is a common divisor for integers p and q given the equation 3p² = q². Participants establish that since q² is divisible by 3, it follows that q must also be divisible by 3. However, the challenge remains in proving that p is also divisible by 3. The conversation highlights the relationship between integer properties and prime factorization, emphasizing that if q is divisible by 3, then rewriting q as 3q' leads to further insights about p.

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If 3p^2 = q^2 and p and q are integers, how do I prove that 3 is a common divisor for p and q?
My attempt: q^2 is divisible by 3, so q is divisible by 3. I can't prove that p is divisible by 3.
 
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Any integer that is not a perfect square has an irrational square root. What can you do with that?
 
Werg22 said:
Any integer that is not a perfect square has an irrational square root. What can you do with that?

Personally, I have no idea what you can do with that.
 
lordy12 said:
If 3p^2 = q^2 and p and q are integers, how do I prove that 3 is a common divisor for p and q?
My attempt: q^2 is divisible by 3, so q is divisible by 3. I can't prove that p is divisible by 3.

Now, just re-write it as p^2 = q^2/3. What does that tell you about p?

Remember, p is an integer so p^2 is also an integer. And q is divisible by 3, but there is only one 3. :wink:

Finish it off from there.
 
Lol, yeah maybe it's not very relevant. Let me repent:

A power has the same prime factors than its root.
 
3|q, rewrite q=3q'
 
oops...I completely disregarded the fact that p and q are integers.

sorry
 

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