3. (2 points) Let D be a domain enclosed by a smooth closed curve y in R?. Assume that the domain D is positively invariant with respect to the dynamics of the planar system x' = f(x,y), y' = g(x,y), where both f and g are differentiable functions. Give an informal argument that if there is no equilibrium point on y, then there must be an equilibrium point inside D. 3. (2 points) Let D be a domain enclosed by a smooth closed curve y in R?. Assume that the domain D is positively invariant with respect to the dynamics of the planar system x' = f(x,y), y' = g(x,y), where both f and g are differentiable functions. Give an informal argument that if there is no equilibrium point on y, then there must be an equilibrium point inside D