[ Eq(Derivative(x1, t), ((-1)*(k1*x1*k9 - k5*x2*k10) + (-1)*k2*x2**k3/(k4**k3 + x2**k3)*x1*k9)/k10),
  Eq(Derivative(x2, t), (1*k8*k9 + 1*(k1*x1*k9 - k5*x2*k10) + (-1)*k6*x2*k11 + 1*k2*x2**k3/(k4**k3 + x2**k3)*x1*k9)/k9) ]