Rapid solution
$$x_{1} = -9$$
=
$$-9$$
=
-9
$$y_{1} = -3$$
=
$$-3$$
=
-3
$$x_{2} = 9$$
=
$$9$$
=
9
$$y_{2} = 3$$
=
$$3$$
=
3
$$x_{3} = - 3 i$$
=
$$- 3 i$$
=
-3*i
$$y_{3} = - 9 i$$
=
$$- 9 i$$
=
-9*i
$$x_{4} = 3 i$$
=
$$3 i$$
=
3*i
$$y_{4} = 9 i$$
=
$$9 i$$
=
9*i