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Math Help - Eqn. of a line

  1. #1
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    Eqn. of a line

    The equation of the line goes through the points (-4, 7) and (4, -7)
    what is the slope?
    What is the B value?

    I keep getting 3/4, which is incorrect.?
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  2. #2
    Junior Member tedii's Avatar
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    Quote Originally Posted by B-lap View Post
    The equation of the line goes through the points (-4, 7) and (4, -7)
    what is the slope?
    What is the B value?

    I keep getting 3/4, which is incorrect.?
    The equation of a slop is m=\frac{y_2-y_1}{x_2-x_1}

    Then you can stick this into the equation y-y_1=m(x-x_1)

    and then put it into slope intercept form y=mx+b
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  3. #3
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    Erm, hai...for what I can see is that you just need to find the slope using the general equation, which is y2 - y1 / X2 - X1...

    And you will get (-14/8),
    then you just use slope equation to find for the equation of line...

    You should get these, y= -7/4...and I think it should not be 3/4
    Aright then, best regards and work hard yeah..me too, haha..
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  4. #4
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    (-4, 7),(4, -7)

    \frac{y - y_1}{y_2 - y_1} = \frac{x - x_1}{x_2 - x_1}

    \frac{y - 7}{-7 - 7} = \frac{x - (-4)}{4 - (-4)}

    \frac{y - 7}{-14} = \frac{x + 4}{8}

    8(y - 7) = -14(x + 4)

    8y - 56 = -14x - 56

    8y = -14x

    y = \frac{-14}{8}x + 0

    The gradient (m) is \frac{-14}{8} and the y-intercept (c or b) is 0.
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  5. #5
    MHF Contributor
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    Talking

    Quote Originally Posted by B-lap View Post
    I keep getting 3/4, which is incorrect.?
    If you show your steps, then we'd be able to help you find the error, so you won't make the same mistake in the future.
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