The centroid of a triangle ABC is at the point (1, 1, 1). If the coordinates of
A and B are (3, -5, 7) and (-1, 7, -6) respectively, find the coordinates of
the point C.
ABC is a triangle whose vertices are (1, 3), (–2, –1) and (4, 0) respectively. G is its centroid and BGCH is a parallelogram. Find the coordinates of the vertex H.