Ex: Determine over which interval(s) the graph is increasing and decreasing. 3 Note: You should also be able to write the intervals of increase and decrease in interval notation. What would the answers above be in interval notation? Pause the video at time-mark 03:52. We will look at two methods for graphing parabolas: 1) Write the function in vertex form (also called standard form). 2) Use the vertex formula.