The equation y = kx represents a linear relationship between two variables, y and x . In this equation, k is a constant that indicates the slope of the line. This means that for every unit increase in x , y changes by k units. If k is positive, the line rises; if negative, it falls. This equation is commonly used in various fields, including mathematics, physics, and economics. It helps to model situations where one quantity depends directly on another, such as calculating cost based on price per unit.