Composition of Transformation
This composition of transformations was performed correctly because, reflections being rigid motions, the pre image and image are congruent. The first reflection is over the line y=-1, the second reflection is over the y axis, and the third reflection is over the line y=-1. These reflections are accurate because if an imaginary line was drawn between corresponding points on the image and its pre image, the line is a perpendicular bisector of the line of reflection and the points are equidistant from the line of reflection. This applies to each step of the composition of transformations.