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    Hello,

    Just posting for some help with a geometry question. 2 Lines which intersect (so finding a shared solution). Essentially simultaneous equations.

    Line l: y = (3/2)x - 3/2
    Line m: y = (-2/3)x + 5

    Solve simultaneously. The question is in the Edexcel C1 book PAGE 88 question 5b).

    Basically I know you have to manipulate the equations so that you can eliminate y. But I don't know whether to subtract or deal with the x fractions first.

    Thanks for any help (if you reply it might help if you quote me).
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    (Original post by TimeWalker)
    Hello,

    Just posting for some help with a geometry question. 2 Lines which intersect (so finding a shared solution). Essentially simultaneous equations.

    Line l: y = (3/2)x - 3/2
    Line m: y = (-2/3)x + 5

    Solve simultaneously. The question is in the Edexcel C1 book PAGE 88 question 5b).

    Basically I know you have to manipulate the equations so that you can eliminate y. But I don't know whether to subtract or deal with the x fractions first.

    Thanks for any help (if you reply it might help if you quote me).
    if they are both equal to y, the right hand sides must be equal ...
    set them equal
    multiply by 6

    etc etc
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    (Original post by TeeEm)
    if they are both equal to y, the right hand sides must be equal ...
    set them equal
    multiply by 6

    etc etc
    I don't know what to do with the fractions sorry.
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    (Original post by TimeWalker)
    I don't know what to do with the fractions sorry.
    after you set the RHS equal to one another multiply the resulting equation by 6

    this will get rid of the halfs and the thirds
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    Ok I eventually get 9x-9 = -4x+ 30
    So 13x = 39, x = 3

    Substituted into Line l:
    y = 3/2(9) - 3/2
    = 9/2 - 3/2
    = 6/2 = 3

    So the intersection is (3,3)
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    (Original post by TimeWalker)
    Ok I eventually get 9x-9 = -4x+ 30
    So 13x = 39, x = 3

    Substituted into Line l:
    y = 3/2(9) - 3/2
    = 9/2 - 3/2
    = 6/2 = 3

    So the intersection is (3,3)
    correct
 
 
 
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Updated: October 31, 2015
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