over k k. Let XX be the affine variety defined by P (t)= N_ K/k (z) P (t)= NK/k (z). We study the
Hasse principle and weak approximation for XX in three cases. For K: k= 4 K: k= 4 and P (t)
P (t) irreducible over kk and split in KK, we prove the Hasse principle and weak
approximation. For k= Q k= Q with arbitrary KK, we show that the Brauer-Manin obstruction
to the Hasse principle and weak approximation is the only one. For K: k= 4 K: k= 4 and P (t) …