[ Eq(Derivative(x1, t), 1*k9*((-x1)/k6 + k5*k4/k6)/k9),
  Eq(Derivative(x2, t), 1*k9*((-x2)/k8 + k7*k4/k8)/k9),
  Eq(Derivative(x3, t), 1*k9*(k10*x10 - k11*x3 - k12*x4*x3)/k9),
  Eq(Derivative(x4, t), 1*k9*k13*x3/k9),
  Eq(Derivative(x5, t), 1*k9*(k14*x3 - k15*x5)/k9),
  Eq(Derivative(x6, t), 1*k9*((x3*x5)**k17/(k16**k17 + (x3*x5)**k17) - k1*x6)/k9),
  Eq(Derivative(x7, t), 1*k9*(k20*x9 - k19*x7 - k2*x7*x10 + k3*x8)/k9),
  Eq(Derivative(x8, t), 1*k9*(k2*x7*x10 - k21*x8 - k3*x8)/k9),
  Eq(Derivative(x9, t), 1*k9*(k1*x6 - k18*x9)/k9) ]