Which polynomial is prime?
x4 3x2 – x2 – 3
x4 – 3x2 – x2 3
3x2 x – 6x – 2
3x2 x – 6x 3

X^4 + 3x^2 - x^2 - 3 = x^2(x^2 + 3) - 1(x^2 + 3) = (x^2 - 1)(x^2 + 3)
x^4 - 3x^2 - x^2 + 3 = x^2(x^2 - 3) - 1(x^2 - 3) = (x^2 - 3)(x^2 - 1)
3x^2 + x - 6x - 2 = x(3x + 1) - 2(3x + 1) = (x - 2)(3x + 1)
3x^2 + x - 6x + 3 = x(3x + 1) -3(2x - 1); since the content of the two bracket are not the same for this polynomial, that mean it is not factorisable and hence a prime.