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