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