What transformation gives the same result as a rotation of 180 around the origin followed by a reflection over the y axis?

A rotation of 180 degrees around the origin followed by a reflection over the y-axis is equivalent to a single transformation: a reflection over the x-axis. This is because the 180-degree rotation negates both the x and y coordinates, and the subsequent reflection over the y-axis negates the x-coordinate again, resulting in a reflection over the x-axis.