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Thread: help with simultaneous equations 3 unknownes

  1. #1
    Newbie
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    Dec 2008
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    help with simultaneous equations 3 unknownes

    hi anyone help me totally stuck on this question thanks first time on forum.
    3r-2t=0.2
    r+s=2.4
    4s-t=7.3
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  2. #2
    Junior Member
    Joined
    Nov 2008
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    Thatīs what I did:
    First eliminate $\displaystyle r$ from the 1st and 2nd equation
    $\displaystyle 3r-2t=0,2$
    $\displaystyle -3r-3s=-7,2$
    $\displaystyle -----------$
    $\displaystyle -3s-2t=-7,0$

    Now eliminate $\displaystyle t$ from this one and the 3rd equation
    $\displaystyle 3s+2t=7,0$
    $\displaystyle 8s-2t=14,6$
    $\displaystyle -----------$
    $\displaystyle 11s=21,6$

    so $\displaystyle s=21,6/11$ I donīt know if you want to give an approximate of that number, if you want its exact value, it is $\displaystyle s=108/55$
    Now you can start the back-substitution in order to get $\displaystyle t$ and $\displaystyle r$

    Hope it helped...
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  3. #3
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    thanks for that big help cheers
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