Exercise
Consider the polynomial d = X2 + 1 in Z/2Z[X]. Three of the following polynomials are in the same residue class modulo d. Which one is the exception?
f1 = 1 + X + X3 +X4.
f2 = 1 + X + X2 +X3 + X4.
f3 = (1 + X)2.
f4 = 1 + X + X2 +X3.