Brent purchased a used vehicle that depreciates under a straight-line method. The initial value of the car is $7500, and the salvage value is $500. If the car is expected to have a useful life of another 7 years, how much will it depreciate each year?

Let the value of the vehicle be described by the equation

V = a + bx

where x = number of years since purchase

a, b are constants.

When x = 0, V = $7500. Therefore

a + b*0 = 7500

a = 7500

When x = 7, V = $500. Therefore

7500 + 7b = 500

7b = 500 - 7500 = - 7000

b = - 7000/7 = - 1000

The equation is

V = 7500 - 1000x

The slope of this equation is the depreciation rate, and it is - $1000 per year.

Answer: $1000 depreciation per year.