Решение систем уравнений второй степени

Решите задачу:

$\left \{ {{y^2-x^2=-6} \atop {y-x=-6(x+y)}} \right. \\ \left \{ {{y^2-x^2=-6} \atop {7y=-5x}} \right. \\ \left \{ {{( \frac{-5x}{7})^2-x^2=-6 } \atop {y= \frac{-5x}{7} }} \right. \\ (\frac{-5x}{7})^2-x^2=-6 \\ \frac{25x^2-49x^2}{49}=-6 \\ -24x^2=-294 \\ 4x^2=49 \\ x_{1}= \frac{7}{2} \\ x_{2}=- \frac{7}{2} \\ y_{1}= \frac{-5* \frac{7}{2} }{7}= -\frac{5}{2} \\ y_{2}= \frac{-5*( -\frac{7}{2}) }{7}= \frac{5}{2}$