Which of the following pairs of sets are equal? Justify your answer.
$A = \{ n : n \in \mathbb{Z} \text{ and } n^2 \le 4 \}$ and $B = \{ x : x \in \mathbb{R} \text{ and } x^2 - 3x + 2 = 0 \}$.

(A) For set $A$,the condition is $n \in \mathbb{Z}$ and $n^2 \le 4$. The integers satisfying this are $\{-2, -1, 0, 1, 2\}$.
For set $B$,the condition is $x \in \mathbb{R}$ and $x^2 - 3x + 2 = 0$. Solving the quadratic equation: $(x-1)(x-2) = 0$,which gives $x = 1$ or $x = 2$. Thus,$B = \{1, 2\}$.
Since $A = \{-2, -1, 0, 1, 2\}$ and $B = \{1, 2\}$,the elements of $A$ and $B$ are not the same.
Therefore,$A \neq B$.