I am curently studying Quantum Field Theory in the large N limit (Eyal, Nishigaki, Moshe, Zinn-Justin) and I am trying to understand how to calculate RG β-function[![large n β-function][1]][1]


How can one reach to such expression from the relation 4.9?[![enter image description here][2]][2]


  [1]: https://i.sstatic.net/2Am7g.png
  [2]: https://i.sstatic.net/zfDTC.png