... I don't understand the concept I think first place so um yea oh and I have an exam tomorrow pls I need help

We know that :
Now using above ideas, we can solve the Problem
[tex](\sqrt{8} + \sqrt{2})^2 = (\sqrt{8})^2 + (\sqrt{2})^2 + 2(\sqrt{8})(\sqrt{2})[/tex]
[tex](\sqrt{8} + \sqrt{2})^2 = 8 + 2 + 2(\sqrt{16}) = 8 + 2 + 2(4) = 10 + 8 = 18[/tex]