Functions and Graphs
Clare Morris, Emmanuel Thanassoulis · 1994
A function expresses a relationship between two or more quantities of interest. For example, we would expect the quantity of bread that people in a certain area will purchase to depend on the price of bread and the population of the area. To describe such a relationship we say that demand for bread is a function of the price and the population. Using D for the quantity demanded, P for the price of bread and S for the size of the population, we can write this function as: D = f(P, S). $${\text{D = f(P, S)}}{\text{.}}$$