with(geom3d):
point(A,1,2,3);
point(B,1,-3,5);
point(C,0,2,4);

line(L1,[A,B]);
detail(L1);

point(T1,0,0,0);
point(T2,1,0,-2);
line(TL1,[T1,T2]);
parallel(L2, C, TL1);
detail(L2);

plane(P1, [A, B, C]);
detail(P1);

plane(P2, [A, [3,0,-1]]);
detail(P2);