Let three vertices be A(3, -4), B(-1, -3) and C(-6, 2) and fourth vertex be D(x, y)
It is given that quadrilateral joining these four vertices is parallelogram.
∴□ABCD is parallelogram
We know that diagonals of parallelogram bisect each other, ie midpoint of the diagonals coincide.
Let E(xm , ym) be the midpoint of diagonals AC and BD.
By midpoint formula,
∴ x = -3 + 1 , y = -2 + 3
∴ x = -2 and y = 1
Hence,
our fourth vertex is D(-2, 1)