ode := -z(t)^2*(diff(P(t),t)/diff(z(t),t)*diff(diff(z(t),t),t)-diff(diff(P(t), t),t))/diff(z(t),t)^2+z(t)*diff(P(t),t)/diff(z(t),t)+(a*z(t)^2+b*z(t)+c)*P(t); z := proc () option remember; 'procname(args)' end proc; z(t) := r*exp( Complex(1)*t);