$$\sqrt{a-2a^{2/2}b^{1/2}+b}-\frac{a-b}{a^{1/2}-b^{1/2}}$$
$\sqrt{-2\sqrt{b}a+a+b}-\sqrt{a}-\sqrt{b}$
$\frac{-a-\sqrt{-2\sqrt{b}a+a+b}+\sqrt{b}}{2\sqrt{b\left(-2\sqrt{b}a+a+b\right)}}$
