Let's say that y is equal to five minus three x over x squared plus three x. And we want to figure out what is the derivative of y with respect to x. Now, it might immediately jump out at you that look, look, y is being defined as a rational expression here, as the quotient of two different expressions. Or you could even view this as two different functions. You could view this one up here as u of x. So you could say this is the same thing. This is the same thing as u of x over, you could view the one in the denominator as v of x.