1) Gathering the data
Cell phone
$400
Depreciates at -17% yearly
Period: 4 yrs
2) Let's write an exponential function to calculate that depreciation:
y = The brand new price x (depreciation rate)^time
17%= 0.17
[tex]\begin{gathered} y=400(1-0.17)^4 \\ y=400(0.83)^4 \\ y=189.83 \end{gathered}[/tex]3) So 4 years from the data of the purchase, the cell phone worths $189.83
