> with(plots):

> A:=implicitplot3d({x1 - x2*z}, x1=-1..1, x2 = -1..1, z = -15..15, style=patchcontour, numpoints=20000):

> B:=implicitplot3d({z+20}, x1=-1..1, x2 = -1..1, z = -20..15, style=patchnogrid, numpoints=1000):C:=implicitplot3d({x1+3*x2}, x1=-1..1, x2 = -1..1, z = -20..15, style=line, numpoints=10000, color=blue):C1:=implicitplot3d({x1^2-x2^2*(x2+0.5)}, x1=-0.9..0.9, x2 = -0.9..0.9, z = -20..15, style=patchnogrid, numpoints=20000, color=blue):

> display(A,B,C1);

> A:=implicitplot3d({x1 - x2*z}, x1=-0.01..0.01, x2 = -0.01..0.01, z = -4..4, style=patchcontour, numpoints=20000):C1:=implicitplot3d({x1^2-x2^2*(x2+0.5)}, x1=-0.01..0.01, x2 = -0.01..0.01, z = -3..3,style=patchnogrid, lightmodel=light2,numpoints=20000,orientation=[12,113]):

> display(A, C1);

>

>