Plot3D[{9,x^2+4 y^2-4 x-8 y+17},{x,0,4},{y,0,2},PlotStyle->{Opacity[0.2]},MeshFunctions->(#1^2+4 #2^2-4 #1-8 #2+17&),RegionFunction->Function[{x,y,z},x^2+4 y^2-4 x-8 y+17≤13],BoxRatios->Automatic,PlotPoints->40]

ContourPlot3D[x^2+y^2+z^2-4x-2y-6z,{x,-4,8},{y,-5,7},{z,-3,9},Mesh->False,ContourStyle->{Opacity[0.2]}]