SOLUTION: math project that i have been struggling with.let x equal the cars age in years and y equal the value after x years. You buy a car for 18000 dollars and after 8 years the car is w

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Question 241725: math project that i have been struggling with.let x equal the cars age in years and y equal the value after x years. You buy a car for 18000 dollars and after 8 years the car is worth 4500 dollars. assuming that the depreciation is linear find an equation which gives the value of the car overtime. find two ordered pairs from the info.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
.let x equal the cars age in years and y equal the value after x years. You buy a car for 18000 dollars and after 8 years the car is worth 4500 dollars. assuming that the depreciation is linear find an equation which gives the value of the car overtime. find two ordered pairs from the info.
:
Find the slope using the slope formula: m = %28y2-y1%29%2F%28x2-x1%29
:
assign the x,y values as follows
x1=0; y1=18000
x2=8; y2= 4500
:
m = %284500-18000%29%2F%288-0%29 = %28-13500%29%2F8 = -1687.5
:
A simple equation
y = -1687.5x + 18000
you can see when x=0 (the year it is new) y = 18000 (price of the car)
Substitute 8 for x
y = -1687.5(8) + 18000
y = -13500 + 18000
y = +4500 which is what we would expect
Ordered pair 8, 4500
:
How about when the car is 10 yrs old (x=10)
y = -1687.5(10) + 18000
y = -16875 + 18000
y = $1125
Ordered pair 10, 1125
:
interesting by this formula, a car becomes valueless in 11 years -562.5
Guess it cost that much to dispose of it!!