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