What are the solutions of the equation x4 – 5x2 – 14 = 0? Use factoring to solve

(x2 - ) (x2 + ) = 0
(x2 - 7) (x2 + 2) = 0
(x2 - 7) = 0 and (x2 + 2) = 0
x2 = 7 and x2 = - 2
√x2 = √7 and √x2 = √-2
x = √7 and x = √-2 --> it doesn't exist