I'm reading Freiligh and he has an example in a book, here it is:
Let $F = R$ and let $f(x) = x^2 + 1$. Which is well known to have no zeros in $R$ and thus is irreducible over $R$ by a theorem previously stated.
Then $<x^2+1>$ is a maximal ideal in $R[x]$. So $R[x]/<x^2 + 1>$ is a field.
This quotient ring is somehow isomorphic with the Complex numbers. I guess I'm having a hard time understanding why that is the case.
Being as simple as possible, can someone explain to me why that is the case. I don't know really advanced math.