The formula is:
$\forall x \; \exists y \; ( y < x \land \forall z (z < x \rightarrow \lnot y < z ))$
The way I understand it, it says for all $x$, there exists a $y$ such that $y < x$ and for all $z$, if $z < x$, then $y \le z$.
For the sets U = $\Bbb Z$ and U = $\Bbb R$, would this be true?
In the case y + 1 = x, that would be true, so there does exist a y. Or am I supposed to see if this is true for all y? (In which case it wouldn't be.)