[ Eq(Derivative(x1, t), (1*k9*k10*k11**k12*k13/(k11**k12 + x3**k12) + (-1)*k9*k14*x1)/k9),
  Eq(Derivative(x2, t), (1*k9*k15*x1*k16/(k16 + x3) + (-1)*k9*k17*x2/(k18 + x2) + (-1)*k9*k19*x2)/k9) ]