If you rewrite the first equation, you will see that it becomes
i.e. exactly the second equation. This causes the system to be underdetermined, since you're asking for the points of intersection of a line with itself, which means all the points of the line.
To graph it, you should graph twice the line . To draw it, sample any two points and connect them. For example, choose
and
to get, respectively,
and
. Then, draw the points
and
and connect them.
