Abstract prime factorization proof

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Homework Help Overview

The discussion revolves around proving that a positive integer \( a > 1 \) is a square if and only if every exponent in its prime factorization is even. The subject area includes number theory and properties of integers.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the definition of prime factorization and the implications of exponents being even. There is an attempt to clarify the structure of the proof by breaking it into two parts, questioning how the properties of squares relate to their prime factorizations.

Discussion Status

Some participants express uncertainty about their progress, particularly regarding the first part of the proof. Guidance has been offered on structuring the proof, and there is a recognition of the need to prove both directions of the "iff" statement.

Contextual Notes

Participants note the importance of distinguishing between the evenness of numbers and the evenness of exponents in the context of the problem. There is also mention of specific examples, such as the prime factorization of 9, to illustrate points of confusion.

kathrynag
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Homework Statement


A positive integer a is called a square if a=n^2 for some n in Z. Show that the integer a>1 is a square iff every exponent in its prime factorization is even.



Homework Equations





The Attempt at a Solution


Well, I know a=p1^a1p2^a2...pn^a^n is the definition of prime factorization.
We let p=2n because any even number squared is an even numbers.
Not sure how to continue.
 
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I keep trying to work on this one on I'm getting nowhere. Am I on the right track or does anyone have a suggestion?
 
It's not an even number; the exponents are even.

So in the prime factorization of a, [itex]{a_1,a_2,...,a_n}[/itex] are even. Now what does that mean about the square root of a?
 
@kathrynag,

When you have an "iff" problem, you really have to solve two problems. Here's a restatement of the problem to make this more clear:
Let a > 1 be an integer.

1. Assume that a is a square. Prove that every exponent in its prime factorization is even.

2. Assume that every exponent in a's prime factorization is even. Prove that a is a square.

Does this help?
 
Petek said:
@kathrynag,

When you have an "iff" problem, you really have to solve two problems. Here's a restatement of the problem to make this more clear:
Let a > 1 be an integer.

1. Assume that a is a square. Prove that every exponent in its prime factorization is even.

2. Assume that every exponent in a's prime factorization is even. Prove that a is a square.

Does this help?
Yeah, that does help. I fell better about the 2nd part of the proof.
The first part still worries me.
Assume n is a square. Then we have a=n^2
That's about as far as I get with that one.
I know what I need to prove, but it's getting there.
n^2=p1^a1p2^a2...pn^an
 
hgfalling said:
It's not an even number; the exponents are even.

So in the prime factorization of a, [itex]{a_1,a_2,...,a_n}[/itex] are even. Now what does that mean about the square root of a?

It is also even.
 
No. Consider 9. Its prime factorization is [itex]3^2[/itex]. Therefore it satisfies the rules of your problem. But it's not even, nor is it the square of an even number.
 
kathrynag said:
Yeah, that does help. I fell better about the 2nd part of the proof.
The first part still worries me.
Assume n is a square. Then we have a=n^2
That's about as far as I get with that one.
I know what I need to prove, but it's getting there.
n^2=p1^a1p2^a2...pn^an

Hint: Write out the prime factorization for n and then use that to come up with another prime factorization for n^2.
 

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