Abstract Algebra: a problem about ideal

In summary, J is the principal ideal (x) in Z[x] and Z[x]/J consists of an infinite number of distinct cosets, one for each n∈Z. A principal ideal is a subset of a ring that is generated by one element and closed under addition and multiplication by elements in the ring. The set generated by {x} in Z[x] is x*Z(x), and the elements in (x) have the form of any polynomial multiplied by x. In Z[x]/J, two elements are in the same coset if their difference is in J. The only elements that remain unchanged after subtracting any polynomial with a zero constant term are those in J.
  • #1
iwonde
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Homework Statement


Let J be the set of all polynomials with zero constant term in Z[x]. (Z=integers)
a.) Show that J is the principal ideal (x) in Z[x].
b.) Show that Z[x]/J consists of an infinite number of distinct cosets, one for each n[tex]\in[/tex]Z.


Homework Equations





The Attempt at a Solution


I have trouble understanding what a principal ideal is. Any help on how I should start would be great. Thanks!
 
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  • #2
Well, what's the set generated by {x} in Z(x)? Isn't it just x*Z(x)? What's that?
 
  • #3
An ideal is a subset of a ring that's closed under addition of its own elements and under multiplication by anything in the ring. A principal ideal is one that's generated by one element.

So, take an element in Z[x] and multiply it by x. Whatever you get, by definition, is in the ideal (x). What do those things look like?

Now, two things are in the same coset of Z[x]/J if their difference is in J. So, if I can subtract off any polynomial I want with zero constant term, what stays unchanged?
 

Related to Abstract Algebra: a problem about ideal

1. What is abstract algebra?

Abstract algebra is a branch of mathematics that studies algebraic structures and their properties. It deals with abstract mathematical objects such as groups, rings, fields, and vector spaces, rather than specific numbers or objects.

2. What is an ideal in abstract algebra?

In abstract algebra, an ideal is a subset of a ring that satisfies certain properties. It is similar to an ideal in everyday language, representing a perfect or idealized version of something. In abstract algebra, ideals can be used to study the structure and properties of rings.

3. How is an ideal different from a subring?

While both ideals and subrings are subsets of a ring, they serve different purposes. An ideal is a subset that is closed under multiplication by elements of the ring, while a subring is a subset that is itself a ring with the same operations as the original ring.

4. What is the importance of studying ideals in abstract algebra?

Ideals play a crucial role in abstract algebra as they allow us to study the structure and properties of rings in a more general and abstract way. They also have applications in other areas of mathematics, such as number theory and algebraic geometry.

5. Can you give an example of a problem about ideals in abstract algebra?

One example of a problem about ideals in abstract algebra is the ideal membership problem, which asks whether a given element belongs to a given ideal. This problem has applications in cryptography and coding theory.

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