How does $-\sqrt {\frac{{2 - \sqrt 2 }}{{2 + \sqrt 2 }}} $ simplify to $1 - \sqrt 2 $? I've the answer for a question in my textbook to be:
$-\sqrt {\frac{{2 - \sqrt 2 }}{{2 + \sqrt 2 }}} $ which i've then simplifed to: $-\sqrt {3 - 2\sqrt 2 } $
However my textbook states $-\sqrt {\frac{{2 - \sqrt 2 }}{{2 + \sqrt 2 }}} =  1 - \sqrt 2 $
How is this?

$$\frac{2-\sqrt{2}}{2+\sqrt{2}}=\frac{2-\sqrt{2}}{2+\sqrt{2}}\frac{2-\sqrt{2}}{2-\sqrt{2}}=\frac{\left(2-\sqrt{2}\right)^{2}}{2}$$
so $$\sqrt{\frac{2-\sqrt{2}}{2+\sqrt{2}}}=\frac{2-\sqrt{2}}{\sqrt{2}}=\sqrt{2}-1$$
