Truth value of a proposition
The predicate whose truth value you're trying to check states the following:


  For every even number $x$ in the list, $x/2$ is also in the list.


This holds in the first case: the even numbers are $-2,0,2$, and indeed $-1,0,1$ are in the list, but not in the second case, since $4$ is in the list but $2$ isn't.