Prove that the following polynomials are irreducible:

Question

Prove that the following polynomials are irreducible:

$x^6 − y(y − 1)x^4 + (y − 1)x^3 − (y^2 − 2y + 1)x + y − 1 \in R[x, y]$

i factor it into $x^6-y(y-1)x^4+(y-1)y^3 -((y-1)^2)x+(y-1) $

I don't know what to do next, is there anything to do $(y-1)$?