The expression "-k(x - x_0)" represents a linear function where "k" is a constant that determines the slope of the line. Here, "x" is the variable, and "x_0" is a specific value of "x" that serves as a reference point. The term "(x - x_0)" indicates how far "x" is from this reference point, and multiplying by "-k" means that as "x" increases, the value of the expression decreases if "k" is positive. This expression is commonly used in various fields, including mathematics, physics, and economics, to model relationships where one quantity decreases as another increases. For example, in physics, it can represent the force acting on an object as it moves away from a certain position, illustrating how forces can change with distance.