Final answer:
To make this set not a function, we would need to add an ordered pair where the x-value is repeated but with a different y-value.
Step-by-step explanation:
In order for a set of ordered pairs to be a function, each input (x-value) must correspond to a unique output (y-value). In this set of ordered pairs (1,4),(2,6),(3,8),(4,10),(5,12), each x-value is unique and has a corresponding unique y-value, so it is a function. To make this set not a function, we would need to add an ordered pair where the x-value is repeated but with a different y-value. For example, we could add the ordered pair (3,9), which would result in duplicate x-values and multiple y-values for the same x-value, violating the definition of a function.