Question 1086066
{{{ x - y^2 = 4 }}}
This is symmettic about the x-axis because ( x, a ) and ( x, -a )
always gives the same {{{ x }}}. 
Here's the plot:
{{{ graph( 500, 400, -2, 16, -6, 6, sqrt( x - 4 ), -sqrt( x - 4 ) ) }}}