If water depths of 58.1, 44.7, 35.6 and 30.8 cm are observed at clock times 19.4, 29.1, 38.8 and 48.5 sec, then at what average rate does the depth change during each time interval?

Sketch a graph of this data set and use a sketch to explain why the slope of this graph between 29.1 and 38.8 sec represents the average rate at which depth changes during this time interval.

 If f(x) = x², give the vertex and the three basic points of the graphs of f(x--.25), f(x) - -1.65, .5 f(x) and .5 f(x--.25) + -1.65. Quickly sketch each graph.