Which vector fields are conservative?
F=⟨y,x⟩\mathbf{F} = \langle y, x \rangleF=⟨y,x⟩
F=⟨−y,x⟩\mathbf{F} = \langle -y, x \rangleF=⟨−y,x⟩
F=⟨2x,2y⟩\mathbf{F} = \langle 2x, 2y \rangleF=⟨2x,2y⟩
F=⟨ex,ey⟩\mathbf{F} = \langle e^x, e^y \rangleF=⟨ex,ey⟩