Question 720953
<pre>
y=3 is this         x=-1 is this        y=x is this         y=-x is this 
green line:         green line:         green line:         green line:
{{{drawing(200,200,-4,4,-4,4,graph(200,200,-4,4,-4,4),
green(line(-5,3,5,3)) )}}}  {{{drawing(200,200,-4,4,-4,4,graph(200,200,-4,4,-4,4),
green(line(-1,-5,-1,5)) )}}}   {{{drawing(200,200,-4,4,-4,4,graph(200,200,-4,4,-4,4),
green(line(-5,-5,5,5)) )}}}   {{{drawing(200,200,-4,4,-4,4,graph(200,200,-4,4,-4,4),
green(line(-5,5,5,-5)) )}}}

You figure out which one is parallel to the y-axis.

Edwin</pre>