So how can we do that using what we know about derivatives? Well, what if we were to figure out an equation for the line that is tangent to the point, to tangent to this point right over here. So the equation of the tangent line at x is equal to four. And then we use that linearization, that linearization to find, to approximate values local to it. And this technique is called local linearization. So what I'm saying is let's figure out what this equation of this line is. Let's call that L of x.