[ Eq(Derivative(x1, t), (1*k17*k2*x3*x5 + (-1)*k17*k3*x1 + (-1)*k17*k4*x1)/k17),
  Eq(Derivative(x2, t), (1*k17*k8*x5/((k10 + x5)*k11*x3) + (-1)*k17*k5*x2*x3)/k17),
  Eq(Derivative(x3, t), ((-1)*k17*k2*x3*x5 + 1*k17*k3*x1 + (-1)*k17*k5*x2*x3 + 1*k17*k1*x3 + (-1)*k17*k6*x3**2)/k17),
  Eq(Derivative(x4, t), (1*k17*k1*x4 + (-1)*k17*k6*x4**2)/k17) ]