Or I could just do this as x minus four squared is equal to zero, or x minus four is equal to zero, so, or where x equals four. So g prime prime of four is equal to zero. So let's see what's happening on either side of that. Let's see if g, if we're actually, if we're actually switching signs or not. So let me draw a number line here. And so this is, so this is two, three, four, five, and I could keep going. And so we know that something interesting is happening right over here.