At clock times 28.2, 42.3, 56.4 and 70.5 sec, we observe water depths of 34.9, 20.1, 10 and 4.6 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 28.2 and 42.3 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--1.25), f(x) - -.65, .2 f(x) and .2 f(x--1.25) + -.65. Quickly sketch each graph.