The sum of ordinates of feet of normals drawn from a point to the parabola, y2 = 4ax is always zero . Now, as normals at three points P, Q and R of parabola y2 = 4ax meet at (h, k). ⇒ The normals from (h, k) to y2 =4ax meet the parabola at P, Q and R. ⇒ y-coordinate y1,y2,y3 of these points and R will be zero. ⇒ y-coordinate of the centroid of ΔPQR i.e.