Finding Increasing and Decreasing Intervals Graphically

Steve is running up the steepest hill in America, Canton Avenue, in Pittsburgh, Pennsylvania. Once he gets to the top he slides down the steep, snowy hill on a sled. The hill is an isosceles triangle with vertex at the top of the hill. If the hill begins at the coordinate $(0,0)$ and the top of the hill is at the coordinate point $(50,50)$, what intervals of Steve's exercises are increasing and what intervals are decreasing?