It is known that there is a line segment AB in the plane rectangular coordinate system, where a (1, 3) b (4, 5). If the vertical coordinates of point A and point B remain unchanged, the horizontal coordinate will be doubled, and the line segment AB _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _. If the vertical coordinates of point A and point B remain unchanged, the horizontal coordinate will become original.