Minimizing Eaug- where did the 2 go?

[ladybird2012]

Hi,
I think I'm missing something really trivial. In slide 11 of lecture 12, I don't see where the 2 went in differentiating lambda*(w^2). In other words, I feel setting Eaug =>0 should result in a 2*lambda*w term...What am I missing?

Thanks.