slope intercept form

Question

A car is worth $16,500 when it is three years old and $12,000 when it is six years old. Construct the equation in slope intercept form that represents the cost of a rental car. 

Answer 1

We lost $4,500 in value over a period of 3 years:

16,500-12,000 = 4500

 

That is a loss of $1500 per year

 

So your slope is m = -1500

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Note:  We have two points: (3, 16500), (6, 12000)

Where x= age of the car in years, y = value of the car.

You can get the slope from the points:

m = (12000-16500)/(6-3) = -1500

 

y = -1500x + b  is the slope intercept form.

Plug in one of the points and solve for b.

 

12000 = -1500(6) + b

12000 = -9000 + b

21000 = b

 

y = -1500x + 21000