Geometric Sequence Problem

Dec 2015
Anaheim, CA
We are working with the explicit formulas for arithmetic AND geometric sequences. I get for the most part, but it is the world problems that stump me a little.

Here's one that confused me that I could use help on:

John buys a computer for 1200 dollars. He predicts that the value of the computer will decrease by 30% every year. Write an explicit formula for this situation and then calculate the value of the computer after 4 years.

Explanation would be greatly appreciated

Prove It

MHF Helper
Aug 2008
If the value decreases by 30% each year, then the value each year is 70% of the previous year. Can you use this to generate your geometric sequence?
Feb 2015
Ottawa Ontario
...or look at it as a crooked Bank paying you -30% annually
on your deposit of 1200 bucks!

Look at it as being the 5th term of a geometric series
with 1st term = 1200 and ratio = -7/10 : got it?
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