Solution
= Solution
The <set difference> consists of elements belonging to the first <set> but not the second:
$$
\boxed{A\setminus B=\{x\in\mathcal U:x\in A\text{ and }x\notin B\}.}
$$
The <symmetric difference> consists of elements belonging to exactly one of the two <sets>:
$$
\boxed{A\oplus B=(A\setminus B)\cup(B\setminus A).}
$$
In particular, the two <sets> in this <union> are <disjoint sets>.