. The three vertices of a parallelogram taken in order are
(–1, 0), (3, 1) and (2, 2) respectively. Find the coordinates of the fourth vertex.
Sol: Let A(–1, 0), B(3, 1), C(2, 2) and D(x, y) be the vertices of a parallelogram ABCD taken in order. Since, the diagonals of a parallelogram bisect each other.
Coordinates of the mid-point of AC = Coordinates of the mid-point of BD
Hence, the fourth vertex of the parallelogram is (–2, 1).