How many 4/5 cup servings are in 4/9 of a cup of yogurt

An architect is designing a water fountain for a park she uses the given function to model the water jet flowing from the fountain nozzles where h(x) gives the height of the water jugs in feet x feet from the starting point h(x)=-1/20x+x+15

In a graph with several intervals o data how does a constant interval appear? what type of scenario produces a constant interval?

Use sigma notation to represent the following series for 9 terms.