집합의 뜻과 포함 관계

Assume that the universal set is the set of integers. Let

$$\begin{aligned}A & = \left\{ { - 3, - 2,2,3} \right\}\!, & B & = \left\{ {x \in \mathbb{Z}\left. \right|x^2 \leq 9} \right\}\!, \\ C & = \left\{ {\left. {x \in \mathbb{Z}} \right|x \geq - 3} \right\}\!, & D & = \left\{ {1,2,3,4} \right\}\!\end{aligned}$$

. In each of the following, fill in the blank with one or more of the symbols $\subset$ , $\subseteq$ , $\not \subseteq$, $=$ , $\ne$, $\in$, $\text{ or } \notin$ so that the resulting statement is true. For each blank, include all symbols that result in a true statement. If none of these symbols makes a true statement, write nothing in the blank.

$\left\{ 1, 2 \right\}$_____$B$