Three given vertices: (0.0,0.0) (2.0,0.0) (2.0,1.0)
Fourth vertex: (0.0,1.0)

Three given vertices: (-3.0,1.0) (2.0,6.0) (-1.0,6.0)
Fourth vertex: (-6.0,1.0)

Three given vertices: (2.5,1.0) (-5.0,-2.0) (-7.0,1.0)
Fourth vertex: (0.5,4.0)

Three given vertices: (2.5,5.0) (2.5,-2.5) (7.0,6.5)
Fourth vertex: (7.0,14.0)