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.