How do we graph transformations that are the reflections?

Line Reflection:
(FLIP) A transformation that creates a figure which are mirror images.
Rule for reflection in the:
x-axis: (x,y) --- (x,-y)
y-axis: (x,y) --- (-x,y)

Reflecting over any line:

Each point of a reflected image is the same distance from the line of reflection as the corresponding point of the original figure.  In other words, the line of reflection lies directly in the middle between the figure and its image -- it is the perpendicular bisector of the segment joining any point to its image.  Keep this idea in mind when working with lines of reflections that are neither the x-axis nor the y-axis.

http://www.regentsprep.org/regents/math/geometry/GT1/reflect.htm