Алгебра: Решить систему уравнений х-у=11 х²-у²=11

Решите задачу:

$\left \{ {{x-y=11} \atop {(x-y)(x+y)=11}} \right. \\\left \{ {{x-y=11} \atop {11(x+y)=11}} \right. \\\left \{ {{x-y=11} \atop {x+y=1}} \right. \\ \left \{ {{x=11+y} \atop {11+y+y=1}} \right. \\ \left \{ {{x=11+y} \atop {2y=-10}} \right. \\ \left \{ {{y=-5} \atop {x=11-5=6}} \right. \\ \left \{ {{x=6} \atop {y=-5}} \right.$