In Dummit and Foote Chapter 13: Field Theory, the authors give several examples of field extensions on page 515 - see attached.
In example (3) we read (see attached)
" (3) Take and , irreducible over by Eisenstein's Criterion, for example"
Now Eisenstein's Criterion (see other attachment - Proposition 13 and Corollary14) require the polynomial to be in R[x] where R s an integral domain.
In example (3) on page 515 of D&F we are dealing with a field, specifically .
My problem is, then, how does Eisenstein's Criterion apply?
Can anyone please clarify this situation for me?