Final answer:
The supremum of a set is the least upper bound. To determine if the supremum exists, you need to check if the set is bounded above and if it has a least upper bound.
Step-by-step explanation:
In mathematics, the supremum of a set is the least upper bound. If a set has a supremum, it means that there is a maximum limit to the set and that limit is included in the set. To determine if the supremum exists for a set, you need to check if the set is bounded above and if it has a least upper bound.
Example: Consider the set A = {1, 2, 3}. The supremum of A is 3 since there is no number greater than 3 in the set A.