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. So this is going to be the same thing as the limit as delta x approaches zero. And I'm gonna rewrite this part right over here. I'm gonna essentially divide and multiply by a change in u.