And if not, what's his mistake? All right, so I'm assuming you've had a go at it. So let's work through this step by step. So over here he's just trying to apply the derivative operator to the expression, which is exactly what he needed to do. He's trying to find the derivative of this thing. And he says, okay, this is a product of two expressions. And then he says, okay, well, this is gonna be the same thing as the derivative, or this is the same thing as the product of the derivatives.