The coefficient in the x3-term is positive, meaning that when x approaches infinity, the graph extends upward.
Since the function is a third-degree polynomial — odd — the left end extends in the opposite direction: downward.
Lastly, let's sketch the rest of the graph. We don't know exactly how it looks, but it intersects the x-axis at x=-21, x=-1 and x=0.
Note that other sketches are possible, as long as the zeros and end behavior are the same.