1.
a. 
is the splitting field of
x5 − 1 over

, and

is separable as char

. By Example 4 §10.1,

where
σ(
u) =
u2 (because

. The lattices are:
Thus
H
is the only intermediate field,

is Galois (as
H
G), and

. We have
σ2(
u) =
u4 =
u−1 so
σ2(
u +
u4) = (
u +
u4). Hence so, since , . Of course
c. splits (x2 + 1)(x2 − 3) over , so it is a Galois extension. Clearly ...