Existence Quantifiers
1. The first problem is to find if there exists an integer $x$ such that $$2x^2 - 4 = 0.$$
2. Start by solving the equation:
$$2x^2 - 4 = 0$$
Add 4 to both sides:
$$2x^2 = 4$$
Divide both sides by 2:
$$x^2 = 2$$
3. Now, find $x$ by taking the square root:
$$x = \pm \sqrt{2}$$
4. Since $\sqrt{2}$ is irrational, there is no integer $x$ that satisfies the equation. So, the statement $(\exists x \in \mathbb{Z})(2x^2 - 4 = 0)$ is false.
5. The second problem is to check if there exists a real number $x$ such that for all real numbers $y$, the equation $$2x + y = 5$$ holds.
6. Rearrange the equation to solve for $y$:
$$y = 5 - 2x$$
7. For the statement $(\exists x \in \mathbb{R})(\forall y \in \mathbb{R})(2x + y = 5)$ to be true, the equation must hold for every $y$ in $\mathbb{R}$.
8. But $y = 5 - 2x$ defines a single value of $y$ for each $x$, not all $y$. So, there is no $x$ such that $2x + y = 5$ for all $y$.
9. Therefore, the statement is false.
Final answers:
- No integer $x$ satisfies $2x^2 - 4 = 0$.
- There is no real $x$ such that $2x + y = 5$ for all real $y$.