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Math Help - Determining equations of lines albebraically

  1. #1
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    Determining equations of lines albebraically

    I'm stuck on these questions and I don't know how to solve.
    With the same x- intercept as 3x-7x+12=0 and parallel to 6x+8y-5=0
    I need to find the equation for this line.

    Also I need the equation for this line.

    With the same x-intercept as y=-2x+10 and perpendicular to 10x+4y+7=0

    Please explain the formula on how you found the equation, thanks.
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  2. #2
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    6x + 8y - 5 = 0

    These are applications of the slope-intercept form. Yo umust know a few things:

    1) y = mx + b - This is the form
    1a) m is the slope
    1b) b is the y-intercept.
    1c) it is important to note that the x-intercept is NOT given in this form.

    2) Parallel lines have the same slope.
    3) Perpendicular lines have slopes with this property (m1)*(m2) = -1

    That is ALL you need for these.

    Put them in slope-intercept form, if possible

    3x - 7x + 12 = 0 ==> x = 3
    6x + 8y - 5 = 0 ==> y = -(3/4)x + (5/8)

    Now the instructions:

    Here's the line: y = mx + b
    1) Same x-intercept as the first. ==> 0 = m(3) + b ==> b = -3m
    Here's the line: y = mx - 3m
    2) Parallel to the second: m = -3/4
    Here's the line: y = (-3/4)x - 3(-3/4) = -(3/4)x + 9/4

    You do the next one.

    Note: I took the problem as presented. If there are typos, you'll get to work the real problem and show us how you did! :-)
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  3. #3
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    First find the x-intercept of this equation

    Quote Originally Posted by buck View Post
    With the same x- intercept as 3x-7x+12=0 {\color{red}\text{should there be a 'y' here somewhere?}}

    Then find the gradient of this line by transposing to y=mx+c

    Quote Originally Posted by buck View Post
    6x+8y-5=0
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  4. #4
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    Give me a sec teachers, I'm like brain blast.
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