The two vertices of parallelogram WXYZ
are W(4, -2) and X(9, 0), and the
intersection of the diagonals is A(6, -4).
Find the coordinates of the other two
vertices.
the diagonals bisect each other.
So the midpoint M is halfway from W to Y and halfway from X to Z
M = (W+Y)/2
Y = 2M-W = 2(6,-4)-(4,-2) = (12,-8)-(4,-2) = (8,-6)
now do Z in like wise.
or, you could just plot the three points and extend the diagonals an equal distance to get to the other vertices.