Question 587785
if r is a root, then (x - r) is a factor


(x - -3i)(x - 3i)(x - -i)(x - i) = 0


(x + 3i)(x - 3i)(x + i)(x - i) = 0


FOILing (two pairs) ___ (x^2 - 9i^2)(x^2 - i^2) = 0


(x^2 + 9)(x^2 + 1) = 0


FOILing ___ x^4 + 10x^2 + 9 = 0



remember, i represents the square root of minus one; so i^2 equals -1