[ Eq(Derivative(x1, t), (1*k28*k19 + (-1)*k28*(k1 + k17*2*x3*k10/x1/(k8 - x3 + k8*k9/x1 + x3*k10/x1 + ((k8 - x3 + k8*k9/x1 + x3*k10/x1)**2 - 4*x3*k10/x1*(k8 - x3))**(1/2)))*x1)/k28),
  Eq(Derivative(x3, t), (1*(k4 + k18*x1 + k20*x3**k6/(k5**k6 + x3**k6)) + (-1)*k27*k2*(1 + x2)*x3)/k27) ]