{ diff(x1, t) = ((-1)*k9*k1*(x1 - x2) + 1*k5*x2*k10 + (-1)*k2*x2^k3/(k4^k3 + x2^k3)*(x1 - x2)*k9)/k10,
  diff(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 }