91Ó°ÊÓ

Endangered species Biologists consider a species of animal or plant to be endangered if it is expected to become extinct within 20 years. If a certain species of wildlife is counted to have 1147 members at the present time, and the population has been steadily declining exponentially at an annual rate averaging 39\(\%\) over the past 7 years, do you think the species is endangered? Explain your answer.

Plutonium-239 The half-life of the plutonium isotope is \(24,360\) years. If 10 g of plutonium is released into the atmosphere by a nuclear accident, how many years will it take for 80\(\%\) of the isotope to decay?

\(\begin{array}{l}{\text { a. Find the inverse of } f(x)=x+1 . \text { Graph } f \text { and its inverse }} \\ \quad {\text { together. Add the line } y=x \text { to your sketch, drawing it with }} \\ \quad {\text { dashes or dots for contrast. }} \\ {\text { b. Find the inverse of } f(x)=x+b(b \text { constant). How is the }} \\ \quad {\text { graph of } f^{-1} \text { related to the graph of } f ?} \\ {\text { c. What can you conclude about the inverses of functions whose }} \\ \quad {\text { graphs are lines parallel to the line } y=x ?}\end{array}\)