GCDs of Polynomials: Reading Rotman's Corollary 3.58

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SUMMARY

The discussion centers on 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. Participants confirm that the gcd is typically understood to be monic by default, implying that if Rotman does not specify "monic," multiple gcds may exist. The clarification sought by the user emphasizes the importance of precise definitions in abstract algebra.

PREREQUISITES
  • Understanding of polynomial algebra
  • Familiarity with the concept of greatest common divisors (gcd)
  • Knowledge of monic polynomials
  • Basic comprehension of abstract algebra principles
NEXT STEPS
  • Review the definition of gcd in Rotman's "A First Course in Abstract Algebra"
  • Study the properties of monic polynomials in algebra
  • Explore examples of gcds in polynomial rings
  • Investigate the implications of non-monic gcds in algebraic structures
USEFUL FOR

Students and educators in abstract algebra, particularly those studying polynomial theory and gcd properties, will benefit from this discussion.

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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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