I am just looking through my course notes right now.

I notice the prof went to multiply two terms and I am kind of lost on the method he used here.

A problem here is that I don't know how to show root of with my keyboard LOL. I am sure someone will

(a+b√2)(c+d√2)=(ac+2bd)+(ad+bc)√2

Is this correct or did I copy something down wrong?