At clock times 34.2, 51.3, 68.4 and 85.5 sec, we observe water depths of 1.3, -21.5, -34.9 and -38.9 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 34.2 and 51.3 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- .75), f(x) - .35, 2 f(x) and 2 f(x- .75) + .35. Quickly sketch each graph.