Nullclines

It is difficult to give a general outline for the determination of nullclines. The key is to set the RHS of each ODE in the system equal to zero and to find all curves on which the resulting equation is satisfied. This material is not found in the text until section 5.2 (it came much earlier in the preliminary edition). You will probably want to close up this section for now.

x-nullclines

y-nullclines