We have this expression being multiplied by this expression. So my brain just says, okay, I have two expressions. Then I'm going to use the product rule. Two expressions being multiplied, I'm going to use the product rule. If it was one expression being divided by another expression, then I would use the quotient rule. But in this case, it's going to be the product rule. And so that tells me that this is going to be the derivative with respect to x of the first expression.