\left \{ {{x(x-6) - x (y + x) = y(3-x)} \atop {2x + y = 0}} \right.
\left \{ {{x^2-6x - xy -x^2) = 3y-xy} \atop {y = -2x}} \right.
\left \{ {{-6x - x(-2x) = 3(-2x)-x(-2x)} \atop {y = -2x}} \right.
\left \{ {{-6x +2x^2 = -6x+2x^2} \atop {y = -2x}} \right.
\left \{ {{0=0} \atop {y = -2x}} \right.
układ nieoznaczony