Question

The number of milligrams D (h) of a certain drug that is in a patients bloodstream h hours after the drug is injected is given by the following function. D (h)=40e ^0.2h When the number of milligrams reaches 9, the drug has to be injected again. How much time is needed between injections? Round your answer to the nearest tenth, and do not round any intermediate computations.

Answer 1

we need to find the value of h when D is 9, so we need to replace D by 9 and find h: