I didn't have an x here. Now I'm taking the derivative with respect to u of x, with respect to this polynomial expression here. So I could just throw the u of x in here if I like. Actually, let me just do that. So this is going to be x to the 3rd plus four x squared plus seven. And then I wanna multiply that, and this is the chain rule. I took the derivative of the outside with respect to the inside, and I'm gonna multiply that times the derivative of the inside.