I have mixed ideas as to how to solve this equation:

2x^4-8x^2+12=0

I found something in my book that says: to solve a 4th degree equation use substitution to rewrite the equation as a quadratic equation. So you'd let u = x^2. However there is a coefficient here, so I wasn't sure how I should attempt to factor it.

I thought about

:

(2x^2 - 6) (x^2-2) = 0 but my answers didn't check. I had (2, -2).

So, I think I'm going to need help (once again). Please provide any formulas or rules that are applicable to equations of this type. Thanks in advance!