Horizontal Parabolas
The graph of the equation y=a(x−h)2+kis a parabola with vertex
(h,k)and the vertical line
x=has its axis of symmetry.
If we subtract k from each side of the equation
y=a(x−h)2+k, and interchange the roles of
x−h and
y−k, the new equation also has a parabola as its graph.