Of course, the denominator is always positive. As x is less than 3, as it's approaching from the left, we are concave upwards. This thing is going to be a positive. f prime prime is greater than 0. We are upwards, concave upwards. When x is just larger than 3, what's going to happen? This first term is still going to be positive, but if x is just larger than 3, x to the fourth is going to be just larger than 81.