{ diff(x1, t) = (1*k10*k1 + (-1)*k10*k4*x1 + 1*k10*k6*(1 - k2*x2)*x2*x1)/k10,
  diff(x2, t) = ((-1)*k10*k3*x2*x1 + 1*k10*k5*x2*(1 - (x2/k7)^k9))/k10 }