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    ray_mezz2002's Avatar
    ray_mezz2002 Posts: 1, Reputation: 1
    New Member
     
    #1

    May 10, 2007, 02:15 PM
    Linear Equations
    :confused: I need help trying to solve linear equations.. I don't even know where to start.. :confused:
    colbtech's Avatar
    colbtech Posts: 748, Reputation: 66
    Senior Member
     
    #2

    May 15, 2007, 02:45 AM
    I presume you have something like:
    2x + 3y = 13
    6x + 4y = 24

    Solve x and y. You need to cancel one of the unknowns.. first multiply all terms in equation 1 by 3. So...

    2x + 3y = 13 becomes 6x +9y = 39

    next subtract equation 1 (new) from equation 2. So...

    6x + 9y = 39 (equation 1 new)
    - 6x + 4y = 24 (equation 2)
    _____________
    5y = 15

    Next divide both sides by 5 to give y...

    y = 15/5
    y = 3

    So now you know y, substitute y into equation 1.

    2x + 3y = 13, which gives 2x + 3*3 = 13
    2x + 9 = 13 (subtract 9 from both sides)
    2x = 13-9
    2x = 4 (divide both sides by 2)
    x = 2

    To check:

    Sustitute the values for x & y into equation 2.

    6x + 4y = 24

    gives (6*2) + (4*3) = 24

    12 + 12 = 24

    Should be able to work out all sorts now. Remember when multiplying 2 negative values the result is positive!
    angelinside94's Avatar
    angelinside94 Posts: 16, Reputation: 1
    New Member
     
    #3

    Jun 22, 2007, 11:13 AM
    Im in the 8th grade and I just passed Algebra and what colbtech just said is exactly how I learned it and I got the Top Academic award so that should help.

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