At clock times 49.4, 74.10001, 98.8 and 123.5 sec, we observe water depths of -57, -93.2, -117.2 and -129 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 49.4 and 74.10001 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) - .85, 5 f(x) and 5 f(x- 1.25) + .85. Quickly sketch each graph.