In mathematics, function is a central idea. Imagine a machine that takes numbered balls from 1 through 26 and labels them with the English alphabet letters A through Z. This machine mimics a mathematical function. A function takes an object from one set A (the input) and maps it to an object in another set B (the output). In mathematics, A and B are usually sets of numbers. In symbols, this relationship is written as f: A → B.

So, a function f is the name of a relationship between two sets. Functions are usually denoted by the letters f, g, or h. A is called the domain (input), and B is called the range (output). If the elements of the domain are denoted by x, and the elements of the range are denoted by y, then a function can also be written as y = f(x...