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Math Help - Help with y=mx+c

  1. #1
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    Question [SOLVED] Help with y=mx+c

    Hello,
    I have come across this problem and need help solving it. Give the equation of the line from (3, -3) to (-1, 3) in the y=mx+c format.
    Last edited by jabelone; April 21st 2012 at 10:29 PM.
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  2. #2
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    Re: Help with y=mx+c

    m is the gradient of the line. So m= (3 minus -3) divided by (-1 minus 3) When you have found m put it into y=mx+c. Now substitute into this x=3 and y=-3 (because you know this point fits the line) and you will get c.
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  3. #3
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    Re: Help with y=mx+c

    thanks,
    So would this be right: y = -1.5 x 3 + 3

    Thank-you for your help, I couldn't find it in my notebook.
    Last edited by jabelone; April 21st 2012 at 10:33 PM.
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  4. #4
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    Re: Help with y=mx+c

    You are correct that m= -1.5 So equation is y= -1.5x + c Now (3,-3) is on this line so -3= (-1.5*3)+c which gives c=1.5

    So equation of line is y= -1.5x+1.5
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  5. #5
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    Re: Help with y=mx+c

    Thank you very much.
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  6. #6
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    Re: Help with y=mx+c

    Another way.
    Once you get the slope of -3/2, you need to find c in (0,c).
    Use one of given poinrs; say (3,-3):
    (-3 - c) / (3 - 0) = -3/2
    -6 - 2c = -9
    c = 3/2
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