Question: Derivatives of Regularized linear regression

On Week 3 Video: Regularized of linear regression, I don’t understand why the summation term from j equals 1 through n disappear after derivation of J(w,b). May you please explain me why?
This equation appears at 7:50 on this video. Thank you!

Hello @Seung_Min_Baek

Welcome to the community.

Please take a look here where we discuss the same topic.

Thank you @shanup ! There’s a very clear explanation.

You are most welcome @Seung_Min_Baek