Hello there,
I hope you and your family are staying safe and healthy during this winter season.

We need to use the Quadratic Formula*
, 
Thus, given the problem:

So now we just need to plug them in the Quadratic Formula*
, 
As you can see, it is a mess right now. Therefore, we need to simplify it
, 
Now that's get us to the final solution:
, 
It is my pleasure to help students like you! If you have additional questions, please let me know.
Take care!
~Garebear
Answer:
<h3>Hope it helps...</h3><h3>have a great day/night</h3>
Answer:

Step-by-step explanation:
7. 
6. 
5. ![\displaystyle 1000[0,85]^8 = 272,490525 ≈ \$272,49](https://tex.z-dn.net/?f=%5Cdisplaystyle%201000%5B0%2C85%5D%5E8%20%3D%20272%2C490525%20%E2%89%88%20%5C%24272%2C49)
4. ![\displaystyle 1000 = a \\ -15\% + 100\% = 1 - r; 85\% = 1 - r \\ 8\:years = time\:[t]](https://tex.z-dn.net/?f=%5Cdisplaystyle%201000%20%3D%20a%20%5C%5C%20-15%5C%25%20%2B%20100%5C%25%20%3D%201%20-%20r%3B%2085%5C%25%20%3D%201%20-%20r%20%5C%5C%208%5C%3Ayears%20%3D%20time%5C%3A%5Bt%5D)
3. ![\displaystyle /text{We need to use the "Exponential Decay" formula} - f(t) = a[1 - r]^t, where a > 0](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%2Ftext%7BWe%20need%20to%20use%20the%20%22Exponential%20Decay%22%20formula%7D%20-%20f%28t%29%20%3D%20a%5B1%20-%20r%5D%5Et%2C%20where%20a%20%3E%200)
2. 
1. 
I am joyous to assist you anytime.