u of c minus u of c is indeed going to be equal to zero. So hopefully you don't feel like it's too much of a stretch, and you can just subtract u of c from both sides and apply properties of limits, and you can get this result as well. But this is interesting, because this essentially can take us to this, that the idea that as our change in x gets smaller and smaller and smaller, as it approaches zero, then our change in our function is also going to approach zero. Now let's just look and take a, let's just graph this or visualize this to get a sense of that. So this is our x-axis. Whoops, that's our x-axis. Let's call that our u-axis maybe.