Show that the system has no closed orbits by finding a Lyapunov .... 1. The problem statement, all variables and given/known data I'm at the point in the problem where I need constants a and b satisfying ax2(y-x3) + by2(-x-y3) < 0 and ax2+bx2 > 0 for all (x,y)≠(0,0). 2. Relevant equations Just in case you're wondering, this is to satisfy the V(x,y)=ax2+by2 > 0 and ΔV(x,y)•<y-x3, -x-y3> < 0 so I can apply that one theorem to my problem. 3. The attempt at a solution Well, it seems reasonable to choose a,b>0 to ensure ax2+bx2 > 0, but I'm having trouble figuring out how to make ax2(y-x3) + by2(-x-y3) < 0 simultaneously.