https://maximummathematics.com/books/foundational-mathematics/logic/quantifiers/index.htmlConsider the following propositional functions, both defined on the universe $\mathcal{U}$ of all integers: \[ \begin{array}{rl} s(n)\text{: } &n^2 \text{ is even.} \\ t(m, n)\text{: } &m^2 - n^2 \text{ is even.} \end{array} \]We can find values of $n$ that make $s(n)$ true, such as $n = -4$. We can also find values of $n$ that make $s(n)$ false, such as $n = 13$. The same is true of $t(m, n)$: the values $m = 3$ and $n = -7$ make $t(m, n)$ true, while $m = 4$ and $n = -1$ make $t(m, n)$ false.Hugoen-US