disc = b^2 - 4a^2 = [-4, 0, 1, 2, -5, 2, 1, 0, -4]
identities over Z: b+2a = (2x^2+3x+2)(x^2-x+1), b-2a = -(2x^4-x^3-x^2-x+2): ok
Res(1+x^4, 1+x+x^2) = 1 (w^3 = 1, 1+w+w^2 = 0 => (1+w^4)(1+w^8) = (1+w)(1+w^2) = 1)
odd primes p < 5000 for which disc is (constant)*(square) mod p: []
p = 2: no root of the form c(1+x)^e, c != 0, |e| <= 4: True
