At clock times 35.8, 53.7, 71.6 and 89.5 sec, we observe water depths of 51.5, 38.9, 32.7 and 32.9 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 35.8 and 53.7 sec represents the average rate at which depth changes during this time interval.

If f(x) = x², what are the vertex and the three basic points of the graphs of f(x--.75), f(x) - 1.85, .2 f(x) and .2 f(x--.75) + 1.85. Quickly sketch each graph.