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