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Thread: I need help with an eqvation system

  1. #1
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    I need help with an eqvation system

    ( 2 / ( x + y ) ) - ( 5 / ( x - y ) ) = -9
    ( 1 / ( x + y ) ) + (3 / ( x - y ) ) = 1

    I'm so sorry but i can't type as you do, but can you try to understand it.
    And thanks in advance.
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  2. #2
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    Re: I need help with an eqvation system

    Put $\displaystyle \frac{1}{x+y}=A,\quadquad \frac{1}{x-y}=B,$

    solve for $\displaystyle A$ and $\displaystyle B,$ and then solve for $\displaystyle x$ and $\displaystyle y.$
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  3. #3
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    Re: I need help with an eqvation system

    I tried that but didn't go far, can you explain more detailed on how to continue from there?
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  4. #4
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    Re: I need help with an eqvation system

    Making the indicated substitutions gets you the equations

    $\displaystyle 2A-5B=-9,$
    $\displaystyle A+3B=1.$

    Solve these for $\displaystyle A$ and $\displaystyle B$ and then substitute into the earlier substitutions.

    $\displaystyle x+y=1/A,$
    $\displaystyle x-y=1/B.$

    You should be able to solve both sets easily.
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  5. #5
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    Re: I need help with an eqvation system

    Oh thanks to you
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