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. We have the function f of x is equal to the square root of x, which is, of course, the same thing as x to the 1 1⁄2 power. So we know what f of two is. We know that f of two, oh, sorry, we know that f of four is.