Answer : (c) (– ∞, 0)
For the function y = \(\frac{1}{\sqrt{|x|-x}} \) to be defined,
| x | – x > 0 as | x | – x ≠ 0
⇒ | x | > x which is only possible when x < 0 as | x | = x for all x ≥ 0.
∴ Domain of y = \(\frac{1}{\sqrt{|x|-x}} \) is x < 0 or (– ∞, 0).