Given the function:
[tex]D(h)=7e^{-.04h}[/tex]we can find how many miligrams will be present after 9 hours by making h = 9 and evaluating on the function to get the following:
[tex]\begin{gathered} h=9 \\ \Rightarrow D(9)=7e^{-0.4\cdot9}=7e^{-3.6}=0.19 \\ \end{gathered}[/tex]therefore, there will be 0.19 miligrams after 9 hours
