write a function that relates two quantities
Try the quiz at the bottom of the page! go to quiz. A function describes the way two quantities are related. y = 2x + 1 is a function as it describes how y relates to x. Every y value is found by doubling the x value and adding 1. Function notation replaces y with f(x) (pronounced f of x) and is written f(x) = 2x + 1. This allows us to use different letters to represent different functions.