MHB GCDs of Polynomials: Reading Rotman's Corollary 3.58

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The discussion centers on the interpretation of Corollary 3.58 from Joseph J. Rotman's "A First Course in Abstract Algebra," specifically regarding the uniqueness of the greatest common divisor (gcd) of two polynomials. The question raised is whether the corollary implies that the gcd is unique only if it is monic. One participant suggests that the gcd is typically defined as monic by default, but advises checking the book's definition for clarity. The conversation emphasizes the importance of precise definitions in abstract algebra. Understanding whether gcds are considered monic is crucial for interpreting the corollary correctly.
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I am reading Joseph J.Rotman's book, A First Course in Abstract Algebra.

I am currently focused on Section 3.5 From Polynomials to Numbers

I need help with the statement and meaning of Corollary 3.58

The relevant section of Rotman's text reads as follows:https://www.physicsforums.com/attachments/4547In the above text (in the statement of the Corollary) we read the following:

" ... ... (ii) Every two polynomials $$f(x)$$ and $$g(x)$$ have a unique gcd. ... ... "
My question (which some may regard as pedantic :) ) is as follows:

Does Rotman actually mean ...

" (ii) Every two polynomials $$f(x)$$ and $$g(x)$$ have a unique monic gcd. ... ... "

Can someone please confirm that my interpretation is correct?

Peter
 
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Peter said:
I am reading Joseph J.Rotman's book, A First Course in Abstract Algebra.

I am currently focused on Section 3.5 From Polynomials to Numbers

I need help with the statement and meaning of Corollary 3.58

The relevant section of Rotman's text reads as follows:In the above text (in the statement of the Corollary) we read the following:

" ... ... (ii) Every two polynomials $$f(x)$$ and $$g(x)$$ have a unique gcd. ... ... "
My question (which some may regard as pedantic :) ) is as follows:

Does Rotman actually mean ...

" (ii) Every two polynomials $$f(x)$$ and $$g(x)$$ have a unique monic gcd. ... ... "

Can someone please confirm that my interpretation is correct?

Peter
I think gcd is defined to a monic by default. Please check the definition in the book. If it doesn't say monic specifically then yes, you can have many gcds.
 
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