If the volume of tetrahedron ABCD is 1 cubic units, where A(0,1,2),B(−1,2,1) and C(1,2,1), then the locus of point D is-
If a variable plane forms a tetrahedron of constant volume 64k3 with the co-ordinate planes, then the locus of the centroid of the tetrahedron is
The locus of the point which is equidistant from the points A (0, 2, 3) and B (2, -2, 1) is: