http://i146.photobucket.com/albums/r...6/problem6.jpg

I tried to simplify it down and go to this point:

http://i146.photobucket.com/albums/r...problem6-1.jpg

I don't know if I did it right. From there, I have no idea what to do T_T The problem asks for a exact answer so everything must stay in radicals. I also don't know how to solve it using matrices...