This is going to be equal to, and I'm color coding it so we can really keep track of things. This is going to be equal to the derivative of the first expression. So I could write that as u prime of x times just the second expression, not the derivative of it, just the second expression. So times v of x. V of x. And then we have plus, plus the first expression, not its derivative, just the first expression, u of x times the derivative of the second expression. Times the derivative of the second expression. So the way you remember it is you have these two things here.