But here, we'll learn about what it is and how and where to actually apply it. So, for example, if I have some function, f of x, and it can be expressed as the quotient of two expressions. So let's say u of x of x over v of x, then the quotient rule tells us that f prime of x is going to be equal to, and this is going to look a little bit complicated, but once we apply it, you'll hopefully get a little bit more comfortable with it. It's going to be equal to the derivative of the numerator function, u prime of x, times the denominator function, v of x, minus the numerator function, u of x, do that in that blue color, u of x times the derivative of the denominator function, times v prime of x. And this already looks very similar to the product rule. If this was u of x times v of x, then this is what we would get when we took the derivative if this was a plus sign, but this is here a minus sign. But we're not done yet.