Posted by **sophia** on Saturday, November 7, 2009 at 11:00pm.

The value of a car decreases at a constant rate as it grows older. When the car is 2 years old, it is worth $23,000. When the car is 5 years old it is worth $15,500.

Write and equation relating y (value of the car $) to x (age of car).

Is it y-23,000=-2500(2)-5 ??

- math -
**Reiny**, Saturday, November 7, 2009 at 11:12pm
so you are looking for a linear relation in the form y = mx + b

where you are given two points

(2,23000) and (5,15500)

so slope = (15500-23000)/(5-2)= 7500/3

= -2500

so y = -2500x + b

sub in the first point

23000 = -2500(2) + b

b = 28000

finally :

y = -2500x + 28000

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