In Exercise, use the viewing windows found in Exercise 1–3.(a) Use the trace feature to es...

In Exercise, use the viewing windows found in Exercise 1–3.

(a) Use the trace feature to estimate the year when the deer population in Exercise 1 first reached 40,000. In what later year was it also 40,000?

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(b) When was the deer population at its maximum? Approximately how many deer were there at that time?

Exercises 1–3

In each of the applied situations in Exercise, find an appropriate viewing window for the equation (that is, a window that includes all the points relevant to the problem but does not include large regions that are not relevant to the problem, and has easily readable tick marks on the axes). Explain why you chose this window. [Hint: You can’t make a negative number of shirts.]

1. Beginning in 1905 the deer population in a region of Arizona rapidly increased because of a lack of natural predators. Eventually food resources were depleted to such a degree that the deer population completely died out. In the equation y = −.125x5 + 3.125x4 + 4000, y is the number of deer in year x, where x = 0 corresponds to 1905.

2. A cardiac test measures the concentration y of a dye x seconds after a known amount is injected into a vein near the heart. In a normal heart

 y = −.006x4 + .14x3 − .053x2 + 179x.

3. The concentration of a certain medication in the bloodstream at time x hours is approximated by the equation

where y is measured in milligrams per liter. After two days the medication has no effect.