Whitman College: David Guichard's "Calculus, Chapter 3: Rules for Finding Derivatives: Section 3.4: The Quotient Rule"
Read Section 3.4 (pages 62-65). As with products, the derivative of a quotient of two functions is not simply the quotient of the two derivatives. In this reading, you will see the quotient rule for differentiating a quotient of two functions. In particular, this will allow you to find the derivative of any rational function.