Có pt (1) $\Leftrightarrow \sqrt{12-2x^2}-3=y+1\Rightarrow 21-2x^2-6\sqrt{12-2x^2}=y^2+2y+1$
Pt (2) $\Rightarrow 2-(y^2+2y+1)=25-20x+4x^2$
$\Rightarrow 2-(21-2x^2-6\sqrt{12-2x^2})=4x^2-20x+25$
$\Leftrightarrow \frac{3}{4}(12-2x^2)+3\sqrt{12-2x^2}+\frac{5}{2}x^2-10x+13=0$
$\Delta = -7.5(x-2)^2\geq 0\Leftrightarrow x=2$
Thử lại .......