# Section 1.4

## Linear Functions of Several Variables

In sections 1.1 through 1.3, we considered functions of one independent variable. The cost, revenue, and profit, were each a function of some quantity Q. If we knew the quantity Q produced and sold, we could use these functions to compute the corresponding cost, revenue and profit at those production levels. As long as we deal solely with one product and the cost, revenue, and profit involved with that product, a function of one variable is adequate. But the total cost, revenue, and profit for a business may come from many products. Each of these products may have its own costs and prices. Using this information we can formulate cost, revenue and profit functions of several variables. Each of these variables represents a quantity of a different product produced and sold by the business.

In this section we’ll learn how to extend what we have learned about a function of a single independent variable to functions of several independent variables.