Finding a splitting field over Q

  • Thread starter Thread starter PsychonautQQ
  • Start date Start date
  • Tags Tags
    Field Splitting
Click For Summary
SUMMARY

The discussion focuses on constructing a splitting field for the polynomial f(x) = x^4 - x^3 - 5x + 5 over the rational numbers Q. The user begins by dividing the polynomial by (x - r), where r is assumed to be a root, leading to a quotient of x^3 + (r-1)x^2 + (r^2-r)x + (r^3 - r^2 - 5). The user identifies 1 as a root based on the sum of coefficients, reducing the polynomial to (x - 1)(x^3 - 5), and concludes that the roots of x^3 - 5 include the cube root of 5 and a third root of unity.

PREREQUISITES
  • Understanding of polynomial division
  • Knowledge of rational roots theorem
  • Familiarity with roots of unity
  • Basic concepts of field extensions in algebra
NEXT STEPS
  • Study polynomial division techniques in detail
  • Learn about the rational root theorem and its applications
  • Explore the properties of roots of unity
  • Investigate field extensions and splitting fields in abstract algebra
USEFUL FOR

Students of abstract algebra, mathematicians working on field theory, and anyone interested in polynomial roots and splitting fields.

PsychonautQQ
Messages
781
Reaction score
10

Homework Statement


I need to construct a splitting field of f(x)=x^4-x^3-5x+5 over Q

Homework Equations

The Attempt at a Solution


So first I will assume r is a root and divide f(x) by (x-r). The quotient came out to be x^3 + (r-1)x^2 + (r^2-r)x + r^3 - r^2 - 5. I am a bit confused what to do now, do i assume another root, call it m perhaps, and do the division again?
 
Physics news on Phys.org
Always check first for obvious integer roots.

Most obvious is: 0 is a root if and only if there is no constant term.

Next most obvious is: 1 is a root if and only if the sum of the coefficients is zero.
 
Last edited:
  • Like
Likes   Reactions: PsychonautQQ
Wow, I didn't know that condition for 1 being a root, thanks! I have now reduced my expression to (x-1)(x^3-5). Will the roots of x^3-5 be the cube root of 5, and then the product of the cube root of 5 with the first and second powers of a third root of unity?
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 28 ·
Replies
28
Views
5K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
6
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 12 ·
Replies
12
Views
5K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K