y-nullclines
And, now, the same general steps for the -nullclines:
> yNULLeqn := factor( rhs(ode2) ) = 0 ;
Thus, the -nullcline consists of the two lines and . Here is how these might be plotted:
> yNULL1 := plot( 0, x=-5..15, color=BLUE ):
> yNULL2 := plot( 20-4*x, x=-5..15, color=BLUE ):
> yNULLplot := display( [ yNULL1, yNULL2 ], axes=BOXED ):
> #yNULLplot;
>