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Math Help - Find the equation of the line joining (0-3), (-5,0)

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    Find the equation of the line joining (0-3), (-5,0)

    Question: Find the equation of the line joining (0-3), (-5,0)

    I encountered a problem when finding the gradient. y2-y1/x2-x1

    If (0, -3) is the x1,y1

    0-(-3)/-5-0 = 3/-5 = -0.6

    If (0, -3) is the x2,y2

    -3-0/0-5 = -3/-5 = 0.6

    Where am I wrong? [Solved]

    My workings for this question:

    Gradient = y2-y1/x2-x1
    = (-3-0)/(0-(-5)
    = -3/5
    = -0.6
    0=-0.6(-5)+b
    0=3+b
    0-3=3-3+b
    -3=b
    Therefore, y=-0.6x-3

    Is my answer correct?
    Last edited by FailInMaths; September 26th 2011 at 09:03 AM.
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    Re: Find the equation of the line joining (0-3), (-5,0)

    Quote Originally Posted by FailInMaths View Post
    Question: Find the equation of the line joining (0-3), (-5,0)

    I encountered a problem when finding the gradient. y2-y1/x2-x1

    If (0, -3) is the x1,y1

    0-(-3)/-5-0 = 3/-5 = -0.6

    If (0, -3) is the x2,y2

    -3-0/0-5 = -3/-5 = 0.6

    Where am I wrong?
    Hi FailInMaths,

    You just made one small error. It should be:

    \frac{-3-0}{0-(-5)}=\frac{-3}{5}=-0.6
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    Re: Find the equation of the line joining (0-3), (-5,0)

    Quote Originally Posted by masters View Post
    Hi FailInMaths,

    You just made one small error. It should be:

    \frac{-3-0}{0-(-5)}=\frac{-3}{5}=-0.6
    Oh yeah! I will try to solve this problem now

    Thanks
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    Re: Find the equation of the line joining (0-3), (-5,0)

    Added my answer for the question

    Can someone check it for me?

    Thanks
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    Re: Find the equation of the line joining (0-3), (-5,0)

    Quote Originally Posted by FailInMaths View Post
    Added my answer for the question

    Can someone check it for me?

    Thanks
    Your answer is indeed correct, but you went to lot of trouble to get there.

    You found the slope to be -.6

    One of your given points was the y-intercept (0, -3).

    Simple substitution into y = mx + b would suffice.

    y = -.6x - 3
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    Re: Find the equation of the line joining (0-3), (-5,0)

    Oh,yeah thanks for point out that and thanks for checking my answer
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    Re: Find the equation of the line joining (0-3), (-5,0)

    Quote Originally Posted by FailInMaths View Post
    Oh,yeah thanks for point out that and thanks for checking my answer
    You're welcome!!
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