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x+y=3, xy=3 Find x^3+y^3. Am I doing it right? Watch

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    xy=3

x+y=3
    I squared x+y=3 to give x^2 + 2xy + y^2 = 3. I then took away 2xy to give x^2 + y^2 = -9. Then multiplied that by x+y=3 to give x^3 + xy^2 + yx^3 + y^3 = -9 which equals x^3 + xy(x+y) + y^3 = -9 then take away xy(x+y) to finally get x^3 + y^3 = -18 but it seems a bit easy. I don't have answers either so I can't tell. Thanks!
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    (Original post by Lulope)
    xy=3

x+y=3
    I squared x+y=3 to give x^2 + 2xy + y^2 = 3. <--------That 3 is wrong.

    It's easier to say y=3-x so x(3-x)=3 and solve that. There are no real solutions by the way.
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