It passes through the origin because the defining characteristic of a proportional relationship is that one variable is a constant multiple of the other.
What is a proportionality relationship
The graph must pass through the origin (0,0) in a proportional relationship between variables x and y, expressed as y = kx. This results from proportionality's basic property, which states that one variable is always a multiple of the other.
The graph's origin, represented by y, is zero when x is zero. In a graphical representation, this represents the origin of the relationship, where both variables have zero quantity. As x increases, y increases proportionately, creating a straight line.
Missing parts;
Why does the graph of a proportional relationship must pass through
origin?