If our second derivative is greater than zero, then we are in this situation right here, we're concave upwards. Where the slope is zero, that's the bottom of the bowl, we have a relative minimum point. And if our second derivative is zero, it's inconclusive. We don't know what is actually going on at that point, so we can't make any strong statement. So with that out of the way, let's just do a quick example, just to see if this has gelled. Let's say that I have some twice-differentiable function h. And let's say that I tell you that h of eight is equal to five. I tell you that h prime of eight is equal to zero.