Final answer:
The equation x - y = 0 indicates that x and y are directly proportional with a constant of proportionality of 1, as y equals x times this constant.
Step-by-step explanation:
The equation x - y = 0 suggests that x and y are directly proportional since rearranging it gives us y = x. This implies that for every unit increase in x, y increases by the same amount, which indicates a more-more relationship. The constant of proportionality here is 1, because y equals x multiplied by 1. If we plot these variables on a graph, we'll get a straight line that goes through the origin (0, 0), confirming their direct proportionality. In general, when two variables x and y are directly proportional, the relationship can be expressed as y = kx, where k represents the constant of proportionality.