I have a simple question regarding nullclines, as I'm having trouble determining the correct direction errors. For example, here's a system of equations: dx/dt = 2-x-y dy/dt=y-x^2 x-null is y= -x + 2 y-null is y= x^2 x-null is vertical, y-null goes horizontal. But when I divide the graph in different sections, and pick different plot points which equations do I plug into to find directions? I know that wasn't clear, but for example: If I want to know if on the y-null if the direction of a certain section is pointing left or right, would I plug the points I chose in: A) dy/dt = y-X^2 B) dx/dt=2-x-y or C) y=x^2 I'm not sure which equation to plug it in. I've tried to think it out, but I end up always confusing myself. Please point me in the right direction. Thanks.