What is the completely factored form of x4 + 8x2 – 9?
(x + 1)(x – 1)(x + 3)(x + 3)
(x + 1) (x minus 1) (x squared + 9)
(x2 – 1)(x + 3)(x – 3)
(x + 1)(x + 1)(x + 3)(x + 3)