You have 15,000 to invest in a retirement account. The fund increases at a rate of 10.8% per year. What will be the value that f the investment at the end of 39 years?

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  .

The answer is c. i think hope this ! can you me with my question ?