How to plot these curves?

Questions
1

curve.jpg
curve.jpg447×405 27.6 KB

how can i plot this using Mathematica?

2

Hi,

a = Plot3D[{x^2 + 3 y^2}, {x, -2, 2}, {y, -2, 2},
   RegionFunction -> 
    Function[{x, y, z},  8 - x^2 - y^2 >=  x^2 + 3 y^2],
   BoxRatios -> Automatic , Mesh -> None, PlotStyle -> Opacity[0.8], 
   PlotRange -> {{-2, 2}, {-2, 2}, {0, 8}}];
b = Plot3D[{8 - x^2 - y^2}, {x, -2, 2}, {y, -2, 2},
   RegionFunction -> 
    Function[{x, y, z}, x^2 + 3 y^2 <=  8 - x^2 - y^2],
   BoxRatios -> Automatic , Mesh -> None, PlotStyle -> Opacity[0.8], 
   PlotRange -> {{-2, 2}, {-2, 2}, {0, 8}}];
c = Plot3D[{0}, {x, -2, 2}, {y, -2, 2},
   RegionFunction -> Function[{x, y, z}, x^2 + 2 y^2 <=  4],
   BoxRatios -> Automatic , Mesh -> None, PlotStyle -> Opacity[0.8], 
   PlotRange -> {{-2, 2}, {-2, 2}, {0, 8}}];
Show[a, b, c]

I.M.