[ Eq(Derivative(x1, t), 0),
  Eq(Derivative(x2, t), (1*k2*k3*k9 + (-1)*k2*k6*x2 + (-1)*k2*(k7*x2*x4 - k8*x5))/k2),
  Eq(Derivative(x3, t), (1*k2*k4*x5 + (-1)*k2*k5*x3)/k2),
  Eq(Derivative(x4, t), (1*k2*k4*x5 + (-1)*k2*(k7*x2*x4 - k8*x5))/k2),
  Eq(Derivative(x5, t), ((-1)*k2*k4*x5 + 1*k2*(k7*x2*x4 - k8*x5))/k2) ]