Irreducible Polynomial of Degree 3

In summary, we are trying to show that if p(x) is of degree 3 and there is no element r∈F that satisfies the equation a0+a1∗r+a2∗r2+a3∗r3 =0, then p(x) is irreducible over F. This is because if p(x) were reducible, there would exist a first degree factor and thus an r that satisfies the equation, which contradicts our assumption. Therefore, p(x) must be irreducible.
  • #1
Justabeginner
309
1

Homework Statement


If p(x) ∈F[x] is of degree 3, and p(x)=a0+a1∗x+a2∗x2+a3∗x3, show that p(x) is irreducible over F if there is no element r∈F such that a0+a1∗r+a2∗r2+a3∗r3 =0.


Homework Equations





The Attempt at a Solution


Is this approach correct?
If p(x) is reducible, then there exists ax + b such that a, b ε F and a≠0. And p(x) = (ax + b)(cx^2 + dx + e). Then an r exists such that p(r) = 0.

Thank you.
 
Physics news on Phys.org
  • #2
Justabeginner said:
Is this approach correct?
Yes, though you could go into a bit more of an explanation as to why there would have to be a first degree factor.
 
  • #3
Justabeginner said:

Homework Statement


If p(x) ∈F[x] is of degree 3, and p(x)=a0+a1∗x+a2∗x2+a3∗x3, show that p(x) is irreducible over F if there is no element r∈F such that a0+a1∗r+a2∗r2+a3∗r3 =0.
With over 300 posts in this forum, you should have learned enough of the ropes here to write exponents clearly.

At the very least, use ^ to indicate exponents, as you do below. Even nicer would be to use the exponent button from the advanced menu - click Go Advanced to show this menu, and then click the X2 to make exponents.

I think what you meant above was p(x) = a0 + a1x + a2x2 + a3x3 = 0, and similarly for your other equation.
Justabeginner said:

Homework Equations





The Attempt at a Solution


Is this approach correct?
If p(x) is reducible, then there exists ax + b such that a, b ε F and a≠0. And p(x) = (ax + b)(cx^2 + dx + e). Then an r exists such that p(r) = 0.

Thank you.
 

What is an irreducible polynomial of degree 3?

An irreducible polynomial of degree 3 is a third degree polynomial that cannot be factored into lower degree polynomials with coefficients in the same field. This means that it cannot be broken down into simpler terms and has no rational roots.

Why is it important to study irreducible polynomials of degree 3?

Studying irreducible polynomials of degree 3 is important because they have many important applications in mathematics and other fields such as engineering and physics. They are also used in cryptography and coding theory.

How can you determine if a polynomial is irreducible of degree 3?

A polynomial of degree 3 can be determined to be irreducible by using the Rational Root Theorem, which states that if a polynomial with integer coefficients has a rational root, it must be a factor of the constant term. If no rational roots are found, then the polynomial is irreducible.

What is the difference between a reducible and an irreducible polynomial of degree 3?

A reducible polynomial of degree 3 can be factored into lower degree polynomials with coefficients in the same field, while an irreducible polynomial of degree 3 cannot be factored. This means that a reducible polynomial can be broken down into simpler terms, while an irreducible polynomial cannot.

Can an irreducible polynomial of degree 3 have complex roots?

Yes, an irreducible polynomial of degree 3 can have complex roots. This is because the degree of a polynomial refers to the highest power of the variable, not the number of distinct roots. An irreducible polynomial can have either real or complex roots.

Similar threads

  • Calculus and Beyond Homework Help
Replies
18
Views
2K
  • Calculus and Beyond Homework Help
Replies
24
Views
800
  • Calculus and Beyond Homework Help
Replies
9
Views
761
  • Calculus and Beyond Homework Help
Replies
12
Views
2K
  • Calculus and Beyond Homework Help
Replies
13
Views
2K
  • Calculus and Beyond Homework Help
Replies
9
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
2K
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
282
  • Calculus and Beyond Homework Help
Replies
11
Views
2K
Back
Top