\[\boxed{\text{924\ (924).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[K\ (0;4):\]
\[1)\ x - y = - 4\ \]
\[2)\ xy = 0\ \ \]
\[3)\ 3x + y = 4\]
\[\boxed{\text{924.\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[A = \left\{ 11;\ - 7;19 \right\}\]
\[\left\{ 11 \right\};\left\{ - 7 \right\};\left\{ 19 \right\};\left\{ \varnothing \right\}.\]