In a traingle ABD, E,F,G are mid points of sides AB,BD,DA respectively. C represents the centroid of the triangle. If BC=9,CG=2x+1, Find x,
The coordinates of the mid-points of sides AB, BC and CA of △ are D (1, 2, -3) E(3, 0, 1) and F(-1, 1, -4) respectively. Write the coordinates of its centroid.