factor x^4-10x^2+9

i need help factoring x^4-10x^2+9

first step:
identify two numbers that multiply to make +9 and add up to -10 ... (-9 and -1, correct?)
(x[sup:3dgb6zn2]2[/sup:3dgb6zn2] - 9)(x[sup:3dgb6zn2]2[/sup:3dgb6zn2] - 1)

this isn't completely factored ... you finish it.