a=1;b=1;c=-1;

Do[Print[a x^2+b y^2+c z^2==r,
ContourPlot3D[a x^2+b y^2+c z^2== Sign[r]r^2,{x,-10,10},{y,-10,10},{z,-10,10},PlotRange->Full,Mesh->False,ImageSize->300]],{r,-2,2}]

A=10;L=10;
Do[Print[A x^2+B y^2==2L z,
ContourPlot3D[A x^2+B y^2==2L z,{x,-10,10},{y,-10,10},{z,-10,10},PlotRange->Full,Mesh->False,ImageSize->300]],{B,-2,2}]