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Math Help - Linear equation

  1. #1
    abc
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    Linear equation

    this is the question:

    Given that A(0,-3) and B(-10,-28) are two points that lie on a straight line in x and y space, find:
    (a) The slope of the line
    (b) The intercept
    (c) The equation for the straight line
    (d) Sketch the line

    I uset his formula c = y1 - y2 / x1 - x2 = 25/10

    so y = a - 25/10x

    the slope of the line is 25/10x

    how do i find the intercept( is there a formuala to this), and also the quation for the stright line.

    I am assuming the "d" will be answered by doing "c" should that shouldn't be a problem.

    I would really appreciate your help.
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  2. #2
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    Quote Originally Posted by abc View Post
    this is the question:

    Given that A(0,-3) and B(-10,-28) are two points that lie on a straight line in x and y space, find:
    (a) The slope of the line
    (b) The intercept
    (c) The equation for the straight line
    (d) Sketch the line

    I uset his formula c = y1 - y2 / x1 - x2 = 25/10

    so y = a - 25/10x

    the slope of the line is 25/10x

    how do i find the intercept( is there a formuala to this), and also the quation for the stright line.

    I am assuming the "d" will be answered by doing "c" should that shouldn't be a problem.

    I would really appreciate your help.
    Im not sure about that form, but i have heard of it, just never learned it. You could use

    y = mx + c

    Where m is the gradient and c is the y-intercept.

    1) Slope of line

    This is the gradient, which is verticle change divided by horizontal change, which if you use your A and B co-ordinates comes to 2.5x. This is what you got, which was 25/10x, but just simplified.

    2) Intercept and Equation of line

    Finding the intercept will basicly find the equation of the line. We know so far that y = 2.5x + c, as the gradient is m, which is 2.5. We then sub in the x and y values for either A or B. If we use A,

    -3 = 2.5(0) + c
    Therefore c = -3

    This means we can sub -3 into c to get the equation of the line.

    y = 2.5x -3

    4) Scetching the line

    This part is quite simple. Just draw a line that goes through points A (0,-3) and B (-10,-28). You can also mark on the line the y intercept, which should be - 3.
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