[ Diff(x[1], t) = (1*k[2]*k[1]*x[4] + (-1)*k[7]*x[1] + (-1)*k[11]*x[1] + (-1)*k[12]*x[1]*x[2])/k[16],
  Diff(x[2], t) = (1*k[4]*x[1] + 1*k[5]*x[3]*x[1] + (-1)*k[8]*x[2])/k[16],
  Diff(x[3], t) = (1*k[6]*x[1] + (-1)*k[9]*x[3])/k[16],
  Diff(x[4], t) = ((-1)*k[1]*x[4] + 1*k[3]*x[3] + (-1)*k[10]*x[4])/k[16],
  Diff(x[5], t) = 0 ]