A quadrilateral has vertices (4, 1), (1, 7), (-6, 0) and (-1, -9). Show that the mid-points of the sides of this quadrilateral form a parallelogram.
Show that A(1, 2), B(4, 3), C(6, 6) and D(3, 5) are the vertices parallelogram. Show that ABCD is not a rectangle.