Quantifier Notation
What's the difference between $\forall \space x \space \exists \space y$ and $\exists \space y \space \forall \space x$ ? I don't believe they mean the same thing even though the quantifiers are attached to the same variable, but I'm having a hard time understanding the difference. Any examples to make the distinction clear would be appreciated.
Solution 1:
Consider this example.
For all $x\neq 0$ there is a $y\neq 0$ such that $xy = 1$.
There is a $y\neq 0$ such that for all $x\neq 0$ you have $xy = 1$.
You can probably see that the one statement is true and the other false.
Solution 2:
Every natural number has a successor. There is no natural number which is the successor of every number.