## greeneyes<3 3 years ago You buy a computer for \$1200. The value of the computer decreases by 30% each year. Find the value of the computer after 4 years. Please show work! Thanks!

1. marshallinwashington

Let c = value of computer in dollars. Let t= the number of years \[c=1200e ^{-.3t}\]\[c=1200e ^{-.3(4)}\] c= \$361.43

2. greeneyes<3

Thanks the only thing is that my teacher got the answer: \$288.12

3. greeneyes<3

Sometimes he is wrong though...

4. marshallinwashington

He probably using a linear equation instead of an exponential. Have you discussed logarithms?

5. greeneyes<3

We did logarithms about 2 months ago.

6. marshallinwashington

Check back a little while and I'll see if I can come up with the linear equation

7. greeneyes<3

okay you can take your time :) really, thanks for helping me. It does mean a lot. :)

8. marshallinwashington

It's not a linear equation, but an exponential equation. \[c=1200(.7)^{t}\] So for t=4 years \[c=1200(.7)^{4}\] Which gives us \$288.12 The difference between the first equation I wrote and the new one is that in the first one the computer lost value continuously.

9. greeneyes<3

Thank you so much!!! ^_^