Finding all complex solutions to this problem

[Cornraker]

Homework Statement

Find all solutions of the equation.

Homework Equations

$$4x^4+25x^2+36=0$$

The Attempt at a Solution

Where do i start here? do i use the quadratic formula? I'm thinking i can factor out a x^2 to make it{$$x^2(4x^2+25x+36)$$ }and from there i can do the quadratic formula. Another question: can i not factor out x^2 since it is not common to all terms because 36 has no $$x^2?$$

 

[Dick]

No, you can't factor x^2 out. You can, on the other hand, substitute u=x^2, solve for u using the quadratic equation and then find x.