y = f(x)

The notation y = f(x) represents a relationship where the value of y depends on the value of x through a specific rule or function, called f. For each input x, the function f tells you how to calculate the corresponding output y. Think of it as a machine: you put in x, and the machine processes it according to a set of instructions (f) to produce y. This notation helps to understand how one quantity changes in relation to another, and it can describe many different kinds of relationships, such as numbers, measurements, or patterns.