Aradioactive isotope has a half-life of 40 years and a radioactivity level of 4 curies. how many years will it take for the radioactivity level to become 0.25?

Answer   (1) u.s.coast guard                (2)president major disaster declaration                (3) 72 hours;                 (4) u.s coast guard auxiliary;

What are your option’s

You're asking in the ap section, so i'll give the ap calculus-style answer. alternatively, you can find the vertex of the parabola and use the "y"-coordinate as the answer.

the maximum height can occur at a critical number, that is, a number  such that  .

the derivative of  can be calculated as follows:



find a value of  that is a zero of the derivative:


this is parabola that is opening downward; we can assume there is a maximum at  .

to find that maximum, calculate  .