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Geometry

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You are given the cordinates of the four points
A (6,2), B(2.4), C (-6, -2) and D (-2,-4).

Show that the equation of the line DA is 4y-3x = -10

help please!!

  • Geometry -

    sub in the points A(6,2) and D(-2,-4)
    into 4y - 3x = -10

    for (6,2)
    LS = 4(2) - 3(6) = -10 = RS
    for (-2,-4)
    LS = 4(-4) - 3(-2) = -10 = RS

    YES , the equation of DA is 4y-3x = -10

    Where do the other two points enter the picture ?

  • Geometry -

    Could you please explain that in full, as im really struggling to understand. The other two points were for calculating gradients AB, CB, DC and DA but i got that.

    Thanks reiny!

  • Geometry -

    Is there a way of simplifying the equation 4y-3x=-10 to y=0.75x - 2.5, then proving that is the equation for DA?

  • Geometry -

    I don't know how much further I can explain it.
    Since both points satisfy the given equation, the equation must be the correct one
    All I did was replace the x and y in the equation with the x and y of each of the points
    LS stands for left side of the equation
    RS stands for the right side.

    in
    4y - 3x = -10
    4y = 3x - 10
    y = (3/4)x - 10/4
    or
    y = .75x - 2.5

    The last equation and the starting equation are really the same thing.
    Subbing in either one gives you the same result

    e.g.
    sub in (6,2) into y = .75x - 2.5
    LS = 2
    RS = .75(6) - 2.5 = 4.5 - 2.5 = 2
    since LS = RS , the point lies on the equation.

    I will let you sub in the second point in the same way.
    Let me know if you did NOT get it.

  • Geometry -

    What is RS and LS?

  • Geometry -

    Did you not read my reply ? I explained what they are.

  • Geometry -

    Im sorry!!! Its so late and im half asleep. Worse time to do maths. I get it reiny!!!!!!!
    Thank you
    So the second point is -4 = -4
    therefore it must be the correct equation as both points satisfy the equation?

  • Geometry -

    You got it.

  • Geometry -

    Your a star!!!!!!!!!!!!!
    Many thanks

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