parentheses vs brackets for indexed family of sets I understand the definition of parentheses and brackets. However this problem involving indexed family of sets has me questioning the definitions.

Q: Let $\mathscr A = \{[-x,0]: x \in \mathbb R \text{ and } 0 &lt; x &lt; 1\}$.
Find the union over $\mathscr A$ and the intersection over $\mathscr A.$

A:  (The union over $\mathscr A$) $= [-1,0]$.
(The intersection over $\mathscr A$) $= \{0\}$.

So, I am confused how the set is defined with $[-x,0]$, and $x$ is restricted by $0 &lt; x &lt; 1$. So, would (the union of $\mathscr A$) $= (-1,0]$?

Thank you in advance!
$(-1,0]$ is correct.

The number $-1$ is not an element of any set in the family $\mathcal{A}$ and therefore cannot be in the union.
$(-1,0]$ is correct.

The number $-1$ is not an element of any set in the family $\mathcal{A}$ and therefore cannot be in the union.