Final answer:
A function is a mathematical relationship that maps inputs to outputs, and to determine if a relation is a function, we need to check if each input has a unique output.
Step-by-step explanation:
A function is a mathematical relationship that maps each element in a set of inputs to exactly one element in a set of outputs. To determine whether a relation is a function, we need to check if each input corresponds to only one output.
For example, if we have the relation {(1, 2), (1, 3), (2, 4)}, we can see that the input 1 is associated with both outputs 2 and 3. Therefore, this relation is not a function.
On the other hand, if we have the relation {(1, 2), (2, 3), (3, 4)}, each input has a unique output, so this relation is a function.