2x^4 + 4x^2
x^4 - 2x^2 - 3
x^4 - 16
x^3 + x^2
x^2 + 6x + 9
x^2 - x - 6
x^2 - 4
x^4 - 10x^2 + 9
(x^2 + 1)(x + \sqrt{3})(x - \sqrt{3}) .
(x + 3)^2
x^2(x + 1)
(x + 2)(x - 2)
(x - 3)(x + 2) .
2x^2(x^2 + 2)
(x^2 + 4)(x + 2)(x - 2)
(x - 3)(x + 3)(x - 1)(x + 1) .