Question 918156
This actually requires a little thought.
Say you are sitting somewhere on this line.
When you look in the direction of the y-axis,
you always see {{{ y = 3 }}}.
Say you happen to be at {{{ x = 137 }}}, and
then you move over so you see {{{ x = 249 }}}.
You look at the y-axis and still see {{{ y = 3 }}}
------------------
The only line that can allow this is a line
parallel to the x-axis and perpendicular to
the y-axis
Here's the plot:
{{{ graph( 400, 400, -10, 10, -10, 10, 3 ) }}}