Three vectors which are not in one plane can not givee zero resultant. This is because resultant of two vectors ( in a plane ) line in their plane. If can not balance the third vector which is in a differet plane.
The resultant of four coplanar vectors can be zero. if they are represented in magbitude and direction by four sides on a polygon taken in the same order. The resultant of four non-coplanr vectors may be zero..
