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