Because where the second derivative is negative, that means our slope is decreasing. We are concave downwards. And where the second derivative is positive, it means our first derivative is increasing. Our slope of our original function is increasing, and we are concave upwards. So notice, we do indeed, the second derivative does indeed cross the x-axis at x equals negative two. It's not enough for it to just be zero or touch the x-axis. It needs to cross the x-axis in order for us to have an inflection point there.