# Math Help - exponential functions

1. ## exponential functions

(a) Niki invested $7000 in the stock market. The investment was a loser, declining in value 11% per year each year for ten years. How much was the investment worth after 10 years? (b) After ten years, the stock began to gain value at 11% per year. After how long will the investment regain its initial value of$7000? Give your answer to the nearest tenth.

I need some help on how to go about this problem, i think the right equation is Q=Qoe^(-kt)...some help

mathlete

2. Originally Posted by mathlete
(a) Niki invested $7000 in the stock market. The investment was a loser, declining in value 11% per year each year for ten years. How much was the investment worth after 10 years? Nothing using e here: $7000(1-0.11)^{10}=A$ Originally Posted by mathlete (b) After ten years, the stock began to gain value at 11% per year. After how long will the investment regain its initial value of$7000? Give your answer to the nearest tenth.
$A(1.11)^n=7000$

Solve for A in the first problem, and then use that to solve for n in the second.