Final answer:
To determine whether a function is a function or not, we need to check if each input has a unique output. If there are any inputs that have multiple outputs or no outputs at all, then the relation is not a function.
Step-by-step explanation:
A function is a relation between a set of inputs and a set of outputs, where each input is related to exactly one output. To determine whether a function is a function or not, we need to check if each input has a unique output.
One way to do this is by creating a mapping diagram or using a table. If there are any inputs that have multiple outputs or no outputs at all, then the relation is not a function.
For example, let's say we have a relation where the inputs are the x-values and the outputs are the y-values. If we have two different x-values that map to the same y-value, then the relation is not a function.