Hi,

let T be the splitting field over \mathbb Q of a polynomial f(x)=x^n+\sum_{i=0}^{n-1} a_i x^i \in \mathbb Q[x], where a_i are integral for the prime numbers 2 and 3 and let f \text{ mod }3 be irreducible.

Now it is said, that 3 is unramified in T.

Please can you explain that to me? I don't understand it.

Bye,
Alexander