Function Definition
A function is a relation in which there is only one y-value for every x-value.
If we given an input of 3 for x, for example, we would only get one output for y, like 1, for example.
Answer
If we look at the table, we can see that the x-value of 3 gives us two outputs: 7 and 9.
Therefore, this relation is not a function.