đặt x=ty$\left\{ \begin{array}{l} (ty)^{2}+ty^{2}+y^{2}=7\\ y^{2}(t^{2}-t-2)=y(2-t) \end{array} \right.$
$\left\{ \begin{array}{l} y^{2}(t^{2}+t+1)=7\\ y^{2}(t-2)(t+1)=y(2-t) \end{array} \right.$ $\rightarrow $t=$\pm$2 $\rightarrow $ y $\rightarrow $ x