It looks like I've kind of, maybe this is a function of x or something, but no, this is just going to be some value. I've inputted c here, and I've evaluated the function of that, and so this is going to be some number. It could be five or seven or pi or negative one, but it's just going to be some value, some constant. So I can treat it like a constant. So this is going to be the same thing as saying the limit as x approaches c of u of x minus u of c is equal to zero. And actually, in the video where we prove that differentiability implies continuity, we started with this, and we proved that right over there. We showed that these two are equivalent things.