Mike bought a car for $40,000 and it decreases in value every year by 15%

Write an exponential function to represent the value of the car at the end of every year. Use the variable x but no commas
f(x)=____
Then fill in the table
x f(x)
0 $__
1 $___
3 $___
5 $___
8 $ ___

1 answer

To model the value of the car as it depreciates over time, we can use an exponential decay function. The general form for such a function is:

\[ f(x) = V_0 \cdot (1 - r)^x \]

where:

  • \( f(x) \) is the value of the car after \( x \) years,
  • \( V_0 \) is the initial value of the car,
  • \( r \) is the rate of depreciation (as a decimal),
  • \( x \) is the number of years.

In this case, the initial value \( V_0 = 40000 \) and the rate of depreciation \( r = 0.15 \).

Thus, the function becomes:

\[ f(x) = 40000 \cdot (1 - 0.15)^x \]

Which simplifies to:

\[ f(x) = 40000 \cdot (0.85)^x \]

Now we can fill in the table for various values of \( x \):

Table of Values:

  • For \( x = 0 \): \[ f(0) = 40000 \cdot (0.85)^0 = 40000 \cdot 1 = 40000 \]

  • For \( x = 1 \): \[ f(1) = 40000 \cdot (0.85)^1 = 40000 \cdot 0.85 = 34000 \]

  • For \( x = 3 \): \[ f(3) = 40000 \cdot (0.85)^3 \approx 40000 \cdot 0.614125 = 24565 \]

  • For \( x = 5 \): \[ f(5) = 40000 \cdot (0.85)^5 \approx 40000 \cdot 0.443705 = 17748.20 \]

  • For \( x = 8 \): \[ f(8) = 40000 \cdot (0.85)^8 \approx 40000 \cdot 0.272490 = 108996 \]

Putting it all together, the filled table is:

\[ \begin{array}{|c|c|} \hline x & f(x) \ \hline 0 & 40000 \ 1 & 34000 \ 3 & 24565 \ 5 & 17748.20 \ 8 & 10899.60 \ \hline \end{array} \]

So the final answers are:

  • f(x) = 40000(0.85)^x
  • The table values filled in would be:
    • 0: $40000
    • 1: $34000
    • 3: $24565
    • 5: $17748.20
    • 8: $10899.60