I would like to prove that x² + 2x - 1 is irreducible over ℤ/5ℤ.
Not really sure how to go with that, it's probably related to finding roots in the field since it's already monic, right ?
Thank you.
I would like to prove that x² + 2x - 1 is irreducible over ℤ/5ℤ.
Not really sure how to go with that, it's probably related to finding roots in the field since it's already monic, right ?
Thank you.
Yes, if a quadratic is reducible, then it factors into two linear factors, so it has at least one root (possibly repeated).
So you can just plug in every number to see if it has a root.