[ Eq(Derivative(x1, t), (1*k17*k18*(k19*x2*k2*x1/(k3 + x1)/(k2*x1/(k3 + x1)*k19 + k5/(k6 + x1)))**4 + (-1)*k17*k20*x1**2/(k21**2 + x1**2) + 1*k17*k22 + 1*k17*k30*(x3 - x1))/k17),
  Eq(Derivative(x2, t), (1*k17*k11/(k12 + x1)*(1 - x2) + (-1)*k17*k2*x1/(k3 + x1)*(k8 + k9*x1)/(k6 + x1)*x2*k23/(k2*x1/(k3 + x1)*k23 + k5/(k6 + x1)))/k17),
  Eq(Derivative(x3, t), (1*k17*k24*(k25*x4*k2*x3/(k3 + x3)/(k2*x3/(k3 + x3)*k25 + k5/(k6 + x3)))**4 + (-1)*k17*k26*x3**2/(k27**2 + x3**2) + 1*k17*k28 + (-1)*k17*k30*(x3 - x1))/k17),
  Eq(Derivative(x4, t), (1*k17*k11/(k12 + x3)*(1 - x4) + (-1)*k17*k2*x3/(k3 + x3)*(k8 + k9*x3)/(k6 + x3)*x4*k29/(k2*x3/(k3 + x3)*k29 + k5/(k6 + x3)))/k17) ]