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Math Help - 3 Simultaneous equations help please.

  1. #1
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    3 Simultaneous equations help please.

    Find the value of k which the simultaneous equations have solutions:
    2y - z = k
    2x + 3y - z = 2
    2x - y + z = 0

    The answer is k = 1 and its done by eliminating x from equations 2 and 3 and getting 4y - 2z = 2....Then comparing that with the first equation.

    BUT... I don't get how you can do that? Because if you eliminate x from one equation, you can't then use that equation to eliminate x in another equation...because it won't have an x?

    Thanks for any help you can offer .
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  2. #2
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    Quote Originally Posted by AshleyT View Post
    Find the value of k which the simultaneous equations have solutions:
    2y - z = k
    2x + 3y - z = 2
    2x - y + z = 0

    The answer is k = 1 and its done by eliminating x from equations 2 and 3 and getting 4y - 2z = 2....Then comparing that with the first equation.

    BUT... I don't get how you can do that? Because if you eliminate x from one equation, you can't then use that equation to eliminate x in another equation...because it won't have an x?

    Thanks for any help you can offer .
    Your eliminating x from two equations to get another equation without x and comparing it to the first, I don't really understand where your confusion is coming form.

    Bobak
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  3. #3
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    Quote Originally Posted by bobak View Post
    Your eliminating x from two equations to get another equation without x and comparing it to the first, I don't really understand where your confusion is coming form.

    Bobak
    Uh, i'm confused as to how you can eliminate x from the two equation.
    Because if you eliminate it from one(giving a total of two equations without x) how would you eliminate it from the 3rd?

    Thanks
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  4. #4
    Member Jonboy's Avatar
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    this is what you should do.

    You have the equations:

     2x + 3y - z = 2
     2x - y + z = 0

    Subtract both equations. That means subtract like terms.

    That means you'll have: 4y -2z = 2

    4y -2z = 2

    Divide both sides by 2: 2y - z = 1

    Look here:
    2y - z = 1
    2y - z = k

    k must be one.
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  5. #5
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    Okey,
    I think i just managed to confuse myself which was why.
    Yea that sounds right, thanks jon and bobak
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