Final answer:
To determine if the given intervals have elements or are empty, we analyze the values of a and b. If a > b, the intervals are empty. If a = b, the intervals may have elements, except for the intervals where the boundaries are the same.
Step-by-step explanation:
For each of the given intervals, the answer depends on the values of a and b. Let's analyze each interval:
- (a, b): Since a > b, this interval does not have any elements and is empty.
- a, b: Similar to the previous interval, if a > b, this interval is also empty.
- a) a, a: This interval has elements if a is a value greater than a, so it is not empty.
- b) a, a: This interval is always empty since the lower and upper boundaries are the same.
- c) (a, a): This interval is also empty because the boundaries are the same and no elements can be included.
- d) (a, a): Similar to the previous interval, this one is always empty as well.