Adaptação Para a Figura 12.2.10

Show[ContourPlot3D[{z==25 - (x^2)- (y^2)},{x,-5,5},{y,-5,5},{z,,25},ContourStyle->{Blue,Opacity[0.15]},MeshFunctions->(#3&),Mesh->{{{0.1},{9},{16},{21},{24}}},MeshStyle->{Red,Thick},PlotPoints->60],Graphics3D[Text[Style["z = 25 - (x^2)- (y^2)",Large],{0,-3,0}]]]