If f(x) = x², what are the vertex and the three basic points of the graphs of f(x- 1.25), f(x) - 1.35, .25 f(x) and .25 f(x- 1.25) + 1.35. Quickly sketch each graph.

At clock times 18, 27, 36 and 45 sec, we observe water depths of 50.1, 36.7, 27.7 and 23.1 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 and 27 sec represents the average rate at which depth changes during this time interval.