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$x$ and $y$ are real numbers where satisfied the equation $x^2+y^2+xy-3x-3y-9=0$

Find the max. and min. values of $x^2+y^2$

I don't know how to find the constraint

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    You should consider accepting the answers to some of your previous questions as well.2012-11-20

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Your constraint is the curve $x^2+y^2+xy-3x-3y-9=0$ Hence, you need to consider the function $f(x,y; \lambda) = x^2 + y^2 + \lambda (x^2+y^2+xy-3x-3y-9)$ and differentiate with respect to $x,y$ and $\lambda$ and find the critical points.

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    oh, thanks a lot2012-11-20