I have a simple question regarding nullclines, as I'm having trouble determining the correct direction errors.(adsbygoogle = window.adsbygoogle || []).push({});

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.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Trouble determining the correct direction errors for nullclines

**Physics Forums | Science Articles, Homework Help, Discussion**