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, .2 f(x) and .2 f(x--1.25) + 1.35. Quickly sketch each graph.

At clock times 7.8, 11.7, 15.6 and 19.5 sec, we observe water depths of 41.3, 38.7, 37 and 36.2 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 7.8 and 11.7 sec represents the average rate at which depth changes during this time interval.