From the rotation formulas, we have $x = \frac{x^{\prime}}{\sqrt{2}} - \frac{y^{\prime}}{\sqrt{2}}$ and $y = \frac{x^{\prime}}{\sqrt{2}} + \frac{y^{\prime}}{\sqrt{2}}$. Substituting these values into the given equation $x^{2}+4 x y+y^{2}-3=0$, we
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