I am trying to wrap my head around the proposition $$\exists x \forall y \exists z \left(\left( y = x + z \right) \lor (z \leq x) \right),$$
where $x, y, z \in \Bbb N^+$.
The proposition is false, but I don't understand why. It is stated as
There is a value $x$ which for every value $y$, there is a value $z$ such that ( = + ) ∨ ( ≤ ),
so I started off with $(x,y,z) = (1,2,1)$, which is true.
Next, I tried $(x,y,z) = (1,3,2)$, which makes
(3 = 1 + 2) ∨ (2 ≤ 1)
T ∨ F = T.
I kept going, but I keep getting True.
It's true since taking $z=x$ the right-hand side (wrt the $\lor$) of the statement $y=x+z \ \lor \ z \leq x$ is always true. It is surely a typo.