[ Diff(x[1], t) = (1*k[7]*k[4]*x[6] + (-1)*k[7]*k[2]*x[3])/k[7],
  Diff(x[3], t) = (2*k[7]*k[3]*x[2]*x[6] + (-1)*k[7]*k[2]*x[3] + (-1)*k[7]*k[1]*x[4])/k[7],
  Diff(x[4], t) = (1*k[7]*k[2]*x[3] + (-1)*k[7]*k[1]*x[4])/k[7],
  Diff(x[5], t) = 0 ]