Answer:
The left side of the parabola is increasing to the maximum, shown on the graph to be (3,6). Then, the right side is decreasing from the max point. The parabola opens down, which means it increases, then decreases.
Explanation:
Always decreasing would mean it took a more linear shape, which this parabola is not doing. It is also not always increasing, because some x,y points are graphed on that curve which go from the center (0,0) to (3,6) back down to (6,0).