`a) y=(\sqrt{x}-1)/(|x|-1)`
ĐKXĐ: `{(x>=0),(|x|-1\ne0):}<=>{(x>=0),(x\ne1),(x\ne-1):}<=>{(x>=0),(x\ne1):}`
Vậy `D=(0;+oo)\\{1}`
`b) y=\sqrt{x+\sqrt{x^2-x+1}}`
ĐKXĐ: `{(x+\sqrt{x^2-x+1}>=0),(x^2-x+1>=0):}<=>`$\begin{cases}x\ge0\\(x-\dfrac{1}{2})^2+\dfrac{3}{4}\ge0∀x\end{cases}⇔x\ge0$
Vậy `D=(0;+oo)`