Factorizing $X^4-Y^2$ in $\mathbb{Q}[X,Y]$ I want to factorize $X^4-Y^2$ in $\mathbb{Q}[X,Y]$ in irreducible factors.
I thought about using Eisenstein's criterium to show that it is irreducible, though I'm not sure what the prime element is in this case. What would that be?

$X^4-Y^2=(X^2-Y)(X^2+Y)$ is the factorization
