We showed that these two are equivalent things. But hopefully you can even think about the intuition. This is just, if the limit as u of x approaches, the limit of u of x as x approaches c is equal to this, then when you evaluate this limit, the limit as x approaches c, well, this thing is going to approach u of c, because we saw it right up here. 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.