Are the following polynomials irreducible over Z2?

Thread starter krispiekr3am
Start date Nov 7, 2006
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Polynomials

In summary, a polynomial is irreducible over Z2 when it cannot be factored into smaller polynomials with coefficients in the field of integers modulo 2. To determine irreducibility, one can check for linear or quadratic factors, use the Eisenstein criterion, or use Berlekamp's algorithm. Knowing if a polynomial is irreducible over Z2 has various advantages in mathematical and scientific applications. It is possible for a polynomial to be irreducible over Z2 but reducible over other fields. To prove irreducibility over Z2, one can use methods such as proof by contradiction or induction.

Nov 7, 2006

krispiekr3am

Are the following polynomials irreducible over Z2?

(a) x2 + x + 1
(b) x2 + 1
(c) x2 + x

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Nov 7, 2006

Hurkyl

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Have you had any thoughts on the problem?

Nov 8, 2006

HallsofIvy

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Z₂ only has 2 elements. Have you checked to see what each of them gives in these polynomials? Finding the roots of p(x)= 0 is often a good way to factor the polynomial p(x)!

And please write at least x^2 for x², not "x2".

Last edited by a moderator: Nov 8, 2006

1. What does it mean for a polynomial to be irreducible over Z2?

When a polynomial is irreducible over Z2, it means that it cannot be factored into smaller polynomials with coefficients in the field of integers modulo 2 (Z2). In other words, the polynomial cannot be broken down into simpler components.

2. How do you determine if a polynomial is irreducible over Z2?

To determine if a polynomial is irreducible over Z2, you can use the following methods:

Check if the polynomial has any linear factors (i.e. degree 1 terms). If it does, then it is not irreducible.
Check if the polynomial has any quadratic factors (i.e. degree 2 terms). If it does, then it is not irreducible.
Use the Eisenstein criterion, which states that if a polynomial has a prime number as its leading coefficient and all other coefficients are divisible by that prime number, then the polynomial is irreducible.
Use the Berlekamp's algorithm, which is a systematic way of checking for irreducibility by factoring the polynomial into smaller polynomials.

3. What are the advantages of knowing if a polynomial is irreducible over Z2?

Knowing if a polynomial is irreducible over Z2 can be useful in various mathematical and scientific applications. For example, it can help in solving equations, finding roots of polynomials, and studying algebraic structures. It can also simplify calculations and make certain problems more manageable.

4. Can a polynomial be irreducible over Z2 but reducible over other fields?

Yes, a polynomial can be irreducible over Z2 but reducible over other fields. The irreducibility of a polynomial depends on the underlying field used. For example, a polynomial that is irreducible over Z2 may have linear factors when viewed as a polynomial over the real numbers (R).

5. How can you prove that a polynomial is irreducible over Z2?

To prove that a polynomial is irreducible over Z2, you can use various methods such as the ones mentioned in question 2. Additionally, you can use proof by contradiction where you assume that the polynomial can be factored into smaller polynomials over Z2 and then show that this leads to a contradiction. You can also use induction to prove that a polynomial of a certain degree is always irreducible over Z2.