Answer:
Step-by-step explanation:
Here, well-defined means that any given object must either be an element of the set, or not be an element of the set. Memorize: We say sets A and B are equal, and write A = B if x ∈ A ⇔ x ∈ B (that is, have exactly the same elements). ... In particular, for each object, what matters is whether or not it belongs to the set.
