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Math Help - System

  1. #1
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    System

    Solve:

    x^3-y^3=602
    xy(y-x)=-198


    Answer:
    x = 11 and y = 9
    or
    x = -9 and y = -11
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  2. #2
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    I will give you two hints:

    (x-y)^3 = x^3 - 3x^2y + 3xy^2 - y^3

    xy^2 - x^2y=-198 \implies -3x^2y+3xy^2=-594
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  3. #3
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    How i find the answer ?
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  4. #4
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    x^3-y^3=602

    -3x^2y+3xy^2=-594

    If we combine the two expressions, we get a perfect cube:
    x^3 - 3x^2y+3xy^2-y^3=602-594 \implies (x-y)^3=8 \implies x - y =\ldots

    This is your key to solving for x and y. Can you do it now?
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  5. #5
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    thank you
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