[ Eq(Derivative(x1, t), 0),
  Eq(Derivative(x2, t), (1*k1*k2/(1 + (x3/k3)**k4) + (-1)*k1*k8*x2)/k1),
  Eq(Derivative(x3, t), (1*k1*k5*delay(x2, k7)**k6 + (-1)*k1*k9*x3)/k1) ]