Factorizing a polynomial over a ring

In summary, the conversation discusses factorizing a polynomial in two different ways in the ring of integers modulo 10. One factorization is given using the roots of the polynomial, while the other factorization is found using a "Master Product rule" involving modular arithmetic. The conversation also considers the possibility of a systematic method for finding all possible factorizations.
  • #1
Adorno
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Homework Statement


Factorize [itex]x^2 + x + 8[/itex] in [itex]\mathbb{Z}_{10}[x][/itex] in two different ways

Homework Equations


The Attempt at a Solution


I can see that x = 8 = -2 and x = 1 = -9 are roots of the polynomial, so one factorization is (x + 2)(x + 9).

Is there a systematic way to find all the factorizations?
 
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  • #2
I just looked at the various ways to get a product of 8 mod 10, the look at the sum of those products. I immediately see that 2*9= 18= 8 mod 10 and 2+ 9= 11= 1 mod 10 and that 4*7= 28= 8 mod 10 and that 4+ 7= 11= 1 mod 10.
 
  • #3
Adorno said:

Homework Statement


Factorize [itex]x^2 + x + 8[/itex] in [itex]\mathbb{Z}_{10}[x][/itex] in two different ways


Homework Equations





The Attempt at a Solution


I can see that x = 8 = -2 and x = 1 = -9 are roots of the polynomial, so one factorization is (x + 2)(x + 9).

Is there a systematic way to find all the factorizations?
It looks like the "Master Product rule"form introductory algebra --- only here you use modular arithmetic.

You are looking for a pair of numbers whose sum is 1 (mod 10) and whose product is 8 (mod 10).
 
  • #4
So, it's essentially just trial and error?
 
  • #5
Adorno said:
So, it's essentially just trial and error?
Yes, but it's somewhat systematic trial & error.
 

FAQ: Factorizing a polynomial over a ring

1. What is factorizing a polynomial over a ring?

Factorizing a polynomial over a ring is the process of breaking down a polynomial into its constituent factors, which are expressions that can be multiplied together to obtain the original polynomial. This process is typically done in the context of abstract algebra, where the ring can be any algebraic structure with operations of addition and multiplication.

2. Why is factorizing a polynomial over a ring important?

Factorizing a polynomial over a ring is important because it allows us to simplify complicated expressions and solve equations. It also helps us understand the underlying structure of the polynomial and its relationship to the ring it is defined over.

3. What are the different methods for factorizing a polynomial over a ring?

There are several methods for factorizing a polynomial over a ring, including factoring by grouping, factoring by trial and error, and using the rational roots theorem. Other methods include factoring by completing the square, using the quadratic formula, and using the difference of squares formula.

4. What is the rational roots theorem?

The rational roots theorem is a method for finding the rational roots (or rational solutions) of a polynomial equation in the form of ax^2 + bx + c = 0. It states that if a polynomial has rational roots, they will be of the form p/q, where p is a factor of the constant term c and q is a factor of the leading coefficient a.

5. Can all polynomials be factorized over a ring?

No, not all polynomials can be factorized over a ring. In some cases, a polynomial may not have any factors that can be expressed in terms of the coefficients of the polynomial. Additionally, certain rings may not have the necessary operations or properties for factorization to be possible.

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