Is it possible that two irreducible polynomials with different variables differ by a constant factor?

I read little bit about Special Relativity and there was one moment that I can't understand.

It was about that there was two irreducible polynomials that have common roots:

I was confused because each of these polynomials have different variables.

My question is: is it possible that two irreducible polynomials (as is shown on the pic.) with different variables differ by a constant factor?

Could anyone provide more easier example with two irreducible polynomials with different variables that differ by a constant?

Thanks.