Which condition for the existence and uniqueness of y′=f(x,y)y' = f(x, y)y′=f(x,y) on RRR is sufficient?
fff is continuous on RRR
fff and ∂f∂y\frac{\partial f}{\partial y}∂y∂f are continuous on RRR
fff is differentiable on RRR
fff is monotonic on RRR