Glide Reflection MBJH Spartans

The three pictures show a pre-image, a middle image, and then a final image. What happened first? How can you tell? Could it go the other way? What changes as you drag point A? What changes as you drag point D? This is called a glide-reflection: A glide reflection is the composition of a translation (a glide) and a reflection across a line parallel to the direction of translation.