Chapter 9.6, Problem 17P

The levels of a certain toxin in a lake have been found to go up and down over time. Biologists are interested in studying the number of freshwater mussels in the lake, the level at the toxin in the lake, and any relationship there may be between the two.

1. Explain why the proposed function with this rule might not be a function: Assign to each amount of the toxin found in the lake, the number of mussels present when there is that amount of toxin in the lake. (Note that in Chapter 15 we will study scatterplots, which are often used to look for associations such as those between toxins and populations,and which can sometimes be approximated by the graph of a function.) .
2. Use words to describe two functions that are relevant to the context of mussels and toxins in a lake.