
Fields
ok here's the 2nd one:
Deduce which of the following are fields:
(i) $\displaystyle \mathbb{F}_5(x)/(x^2 + 2x + 2)$
(ii) $\displaystyle \mathbb{F}_5(x)/(x^2 + 2)$
(iii) $\displaystyle \mathbb{F}_5(x)/(x^2 +3)$
(iv) $\displaystyle \mathbb{F}_5(x)/(x^2 + 4)$
Show that $\displaystyle \mathbb{F}_5(x)/(x^2 + 2)$ and $\displaystyle \mathbb{F}_5(x)/(x^2 + 3)$ are isomorphic as rings.
for part (i) to (iv), im guessing i have to draw out their additive and multiplicative tables and deduce that all polynomials have remainder inverses for them to be fields? is this correct? or are there any other suggestions? thnx :)

$\displaystyle F[x]/(p(x))$ is a field for nonconstant polynomial if and only if p(x) is irreducible.