Re: once quasi asked about unions of sets ...

In article <d3n3e3luublpm0cvlguhngk2eu4or1c61g@xxxxxxx> quasi@xxxxxxxx writes:
2x U 3x = 0 mod 6 U 2 mod 6 U 3 mod 6

You forgot one: U (4 mod 6)

seems very similar !!

Well, you have a good point.

And in another article I gave the simple outline of a proof that there is
no polynomial that will work.

However it's easy to prove that a univariate polynomial can't work.

Indeed. If you have two polynomials f(x) and g(x) of degree n and m,
if there is a polynomial such that range(f) U range(g) = range(h) than
h can not have degree larger than max{n,m}.

I don't think 2 variables will work either, but I don't have a proof
of that.

But more variables provide lots of flexibility, so who knows?

Indeed. There is a polynomial with many variables, that (when the
result is positive) gives only primes as result.
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