Dilating a quadrilateral

Dilation is a technique for creating similar figures. Each point is stretched outwards from the center point D by multiplying distances by the scale factor (Outwards if the scale factor is bigger than 1.) Move the points A, B, C, D to change the shape of the quadrilateral. Move the center point E to dilate from a different location. Use the slider to change the scale factor.
To understand how dilation produces similar figures, see Dilating a triangle on GeoGebraTube: http://ggbtu.be/m2742017