restart;
f:=(x,z)->x+z;

g:=(x,z)->1-x^2;

A1:=solve(f(x,z)=g(x,z),x);

b:=unapply(A1[1],z);

a:=unapply(A1[2],z);

c:=1; plot([f(x,c),g(x,c)],x=a(c)..b(c));

plot3d([f(x,z),g(x,z)],z=-2..1,x=a(z)..b(z));

plot3d(sqrt(x),theta=0..2*Pi,x=0..4,coords=cylindrical);

plot3d([sin(x)+5,1],theta=0..2*Pi,x=0..10,coords=cylindrical);

plot3d([2/x,4/x],theta=0..2*Pi,x=1..3,coords=cylindrical);