[ Diff(x[1], t) = (1*k[9]*k[1] + (-1)*k[9]*k[2]*x[1]*x[2]^k[4]/(k[3]^k[4] + x[2]^k[4]))/k[9],
  Diff(x[2], t) = (1*k[9]*k[5]*(1 - x[2])*x[1]^k[8]/(k[7]^k[8] + x[1]^k[8]) + (-1)*k[9]*k[6]*x[2])/k[9] ]