So we're gonna differentiate this with respect to x. We could write this as the derivative of y with respect to x, which is going to be equal to the derivative of y with respect to u times the derivative of u with respect to x. This is what the chain rule tells us. But how do we actually go about proving it? Well, we just have to remind ourselves that the derivative of y with respect to x, the derivative of y with respect to x, is equal to the limit as delta x approaches zero of change in y over change in x. Now we can do a little bit of algebraic manipulation here to introduce a change in u. So let's do that.