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. Now this is a problem. You are probably familiar, if I take the derivative of the sum of two things, so the derivative with respect to x of f of x plus g of x, that indeed is equal to the derivative of the first, f prime of x, plus the derivative of the second. But that is not true if we are dealing with the product of functions.