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Math Help - lines an equations

  1. #1
    Newbie pianogurl1250's Avatar
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    Question lines an equations

    ok another question...

    i need to find out an equation of a line that contains the point (-2,5) and is parallel to the line y=4x-3

    if someone could pls tell me how to go about this it would be very helpful cuz as usual im stuck!
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  2. #2
    TD!
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    If the equation of a line is of the form y = ax + b, then a is the slope.
    Find the slope of the given line, since parallel lines have the same slope, you have then found a.
    To determine b, fill in the given point for x and y, this will give a lineair equation in b which you can solve.

    Also possible: the line with slope a through the point (p,q) is given by: y-q = a(x-p).
    Last edited by TD!; January 14th 2006 at 09:20 AM.
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  3. #3
    Grand Panjandrum
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    Quote Originally Posted by pianogurl1250
    ok another question...

    i need to find out an equation of a line that contains the point (-2,5) and is parallel to the line y=4x-3

    if someone could pls tell me how to go about this it would be very helpful cuz as usual im stuck!
    A line parallel to y=4x-3 has slope or gradient equal to the
    gradient of this line, so the required gradient is 4.

    Therefore the equation of the line is something like:

    y=4x+c,

    for some c. The value of c can be determined as
    it passes through (-2,5). To do this we put y=5 and
    x=-2 into the above equation and then solve for c, ie solve:

    5=4 \times (-2) +c

    for c.

    RonL
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