We know that this is positive two. The principal root of four is positive two. So you say, okay, this is going to be a little bit more than two. But let's say that we want to get a little bit more accurate. And so what I'm going to show you in this video is a method for doing that, for approximating the value of a function near a value where we already know the value. So what am I talking about? So let's just imagine that we had the function.