If f(x) = x², what are the vertex and the three basic points of the graphs of f(x- .25), f(x) - -1.15, 5 f(x) and 5 f(x- .25) + -1.15. Quickly sketch each graph.

At clock times 18.6, 27.9, 37.2 and 46.5 sec, we observe water depths of 36.5, 25.8, 20.1 and 19.4 cm.

• At what average rate does the depth change during each time interval?

Sketch a graph of depth vs. clock time.

• Use a sketch to explain why the slope of this graph between 18.6 and 27.9 sec represents the average rate at which depth changes during this time interval.