I think this is right...
Say $ F = Z_2[x]/<x^5 + x^3 + 1> $
Then F = {$ ax^4 + bx^3 + cx^2 + dx + e $ | a, b, c, d, e in $ Z_2 $}
So |F| = 32 and |F*| = 31
This means F* is isomorphic to $ Z_{31} $. Since 31 is prime, all non-identity elements in $ Z_{31} $ are generators. This means that all non-identity elements in F* are generators. So, x is a generator of F*
