Three points of a parallelogram are (4, 3), (-4 3), and (2, -3).
What are the coordinates of the 4th point that would complete the parallelogram?
Note that the first two points lie on a horizontal line, y=3
So the easiest way to complete the parallelogram is to make sure the other two points lie on the line y = -3
And since the 1st two points are 8 units apart, the last point is (-6,-3)
But it is also possible to find a different point. (2,-3) and (4,3) lie on a line with slope 1. Since (4,3) = (2,-3)+(2,6) the last point is (-4,3)+(2,6) = (-2,9)