I understood but I have a doubt here.
When y = x, the line goes through the middle (0,0) in the right direction in the graph, then why does the line go through the middle (0,0) in the left direction in the graph, when y = -x? I mean both lines should be in the same direction either in the right direction or in the left direction because the two equations ( y = x and y = -x ) shows same values 0,0 ( if x = 0, y = 0) and 0,0 ( if x = 0, y = -0 = 0). I am confused here. Could you explain, please?