{ diff(x1, t) = (1*k9*k1*x1*(1 - x1/k2) + (-1)*k9*k3*x1*x3/(k4 + x3))/k9,
  diff(x2, t) = 0/k9,
  diff(x3, t) = (1*k9*k6*x2*x1/(x1 + k5) + (-1)*k9*k7*x3 + (-1)*k9*k8*x1*x3)/k9 }