So each of these are going, this value right over here, let me make these color-coded maybe, so this orange delta x, this orange delta x is going to be the negative of this green, of this green delta x. This is the negative of that right over there. And everything else is the same. So what am I going to end up doing? Well, I'm essentially going to end up having the negative value of this. So this is going to be equal to the negative of the integral from a to b of f of x dx. And so this is the result we get, which is another really important integration property that if you swap, if you swap the bounds of integration, and it really just comes from this idea.