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Math Help - Slope-Intecept Form X-Intercept distance

  1. #1
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    Slope-Intecept Form X-Intercept distance

    A line with slope 2 intersects a line with slope 6 at the point (40,30). What is the
    distance between the x-intercepts of these lines? How is the answer 10?
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  2. #2
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    Here is the way I would do it.
    y=2x+b
    30=2(40)+b
    30=80+b
    -50=b
    y=2x-50

    then y=6x+b
    30=6(40)+b
    30=240+b
    -210=b
    y=6x-210

    we have y=2x-5 and y=6x-210
    0=2x-5 and 0=6x-210
    5=2x 210=6x
    x=5/2 x=35
    total answer of 32.5 but it is supposed to be 10 what am i doing wrong?
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  3. #3
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    Quote Originally Posted by sundance240 View Post
    A line with slope 2 intersects a line with slope 6 at the point (40,30). What is the distance between the x-intercepts of these lines? How is the answer 10?
    Suppose that (a,0) is the x-intercept of the line with slope 2.
    Suppose that (b,0) is the x-intercept of the line with slope 6.
    Now use the slope formula: 30/(40-a)=2 & 30/(40-b)=6.
    Solve for a & b.
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  4. #4
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    Hello, sundance240!

    A silly error . . .


    Here is the way I would do it.

    y .= .2x + b
    . . 30 .= .2(40) + b . . b = -50
    . . y .= .2x - 50


    y .= .6x + b
    . . 30 .= .6(40) + b . . b =-210
    . . y .= .6x - 210

    . . . . . . . . . . . . . . .
    We have: .y .= .2x - 5 . . . y .= .6x - 210
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