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Math Help - System of linear equations.

  1. #1
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    System of linear equations.

    Hi! This is my first post and hopefully someone will be able to help me! I have tried this problem atleast 10 times but I am just getting frustrated... it's not working! Here it is:

    you have to solve for x, y, and z.. and I could get one but then it doesnt work for the other problems...

    2x+y+z=4

    3x-y+4z=11

    x-y+5z=20
    Last edited by mr fantastic; October 30th 2010 at 12:34 AM. Reason: restored original post, re-titled.
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  2. #2
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    If you combine the first and second you can get 5x+5z=15.

    If you combine the second and third you can get 2x-z=-9.

    Can you solve that two variable system?
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  3. #3
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    THANKS!I got :
    x=2
    z+1
    y=-7

    Am I correct?? HOW did you do that?! I have tried and tried with no luck.. at one point I thought x=4 so maybe I just needed to divide or something.. Maybe I'm not a lost cause after all! THANKS so much!
    Last edited by Jhevon; October 29th 2010 at 05:10 PM. Reason: restored old post
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  4. #4
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    Thanks!
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  5. #5
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    I think I got it now! I got a little excited before that you made progress and I missed the (-)! NOW this is what I got:

    x= -2
    y=3
    z= 5

    ? Howd I do? THANKS so much! Sorry If im posting too much I'm just so glad to have this answer!
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  6. #6
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    Correct. To see if you're correct, simply substitute your values
    in one of the original equations; OK?
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  7. #7
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    Thank you so much! VERY much appreciated!! If I may ask how long did it really take you to do that? I sat literally for 45 minutes trying to do it and no luck! But I did find that on my paper what Plato wrote so I need to pay more attention to the (-) and such. Thanks again!
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