And now let's think about continuity. So let's first think about continuity. And frankly, if it isn't continuous, then it's not going to be differentiable. So let's think about it a little bit. So in order to be continuous, f of, let me use a darker color, f of three needs to be equal to the limit of f of x as x approaches three. Now what is f of three? Well, let's see, we fall into this case right over here, because x is equal to three.