This polygon was rotated 180 degrees counter - clockwise around the origin. If the graph was not there, you could check if the rotation was correct by looking at the pre-image and image. Each vertex of the pre-image will move the same degree and direction around the center of rotation. The pre-image and image vertices are the same distance from the center. Examples of rotations are turns in a car, a clock, and opening a door (the hinges are the center point).