Answer: Proportional is two varying quantities are said to be in a relation of proportionality, if they are multiplicatively connected to a constant, that is, when either their ratio or their product yields a constant. The value of this constant is called the coefficient of proportionality or proportionality constant.
In this case the method of there being two of the same x values it is NOT a function. Because then there will be two points on top of each other resulting in it not passing the vertical line test on a graph.
