#4.1.7

var("x", "v", "a")
xprime=v
vprime=-x-(a*v^3-v)
vprime_1=-x-(5*v^3-v)
vprime_2=-x-(12*v^3-v)
vprime_3=-x-(6*v^3-v)
t=srange(0,10,0.1)
sol=desolve_odeint([xprime, vprime], ics=[1,1], dvars=[x,v], times=t)
sol_1=desolve_odeint([xprime, vprime_1], ics=[1,1], dvars=[x,v], times=t)
sol_2=desolve_odeint([xprime, vprime_2], ics=[1,1], dvars=[x,v], times=t)
sol_3=desolve_odeint([xprime, vprime_3], ics=[1,1], dvars=[x,v], times=t)
list_plot(sol_1)
list_plot(sol_2)
list_plot(sol_3)