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Math Help - linear equation

  1. #1
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    Feb 2008
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    linear equation

    Please help. I'm math retarded. These are some math questions I can't figure out.


    You purchase an SUV for $26,000. A year later, the car is worth only $24,800.If the value of the car continues to depreciate at that rate,

    A) find the linear equation that determines the value of the car based on the number of years you own it.


    B) when will the car be worth $500?



    thanks for any help
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  2. #2
    Senior Member topher0805's Avatar
    Joined
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    Standard Equation of a line is:

    y = mx+b

    Where m is the slope and b is the y-intercept.

    The first thing to do is find the slope. Recall the slope formula:

    <br />
slope = \frac {rise(y)}{run(x)}

    In this case we know that when the x variable has changed 1 unit, y has decreased by 1,200. So, the slope is:

    -1,200

    We also need the y intercept. This is at x=0. We know that the car is originally worth 26,000 dollars so our y intercept is:

    26,000

    Plug it in to our standard equation to get:

    <br />
y = -1,200x + 26,000

    The car will be worth $500 when y = 500 so just set the equation equal to 500:

    -1,200x + 26,000 = 500

    And solve for x.
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