1) $y = \frac{2x - 3}{x + 4}$

2) $y = \frac{x - 2}{x^2 - 5x + 1}$

3) $y = \frac{5 - x^2}{x^2 - 5x - 2}$

4) $y = \frac{x^2 - 3}{(x - 1)(x^2 - 2x)}$

5) $y = \frac{4 - x^2}{x^2 + x - 2}$

6) $y = \sqrt{x - 2}$

7) $y = \sqrt{4 - 2x}$

8) $y = \sqrt{x^2 - 4}$

9) $y = \sqrt{1 - x^2}$

10) $y = \sqrt{2 - x^2}$

11) $y = \sqrt{x^2 - 4x - 1}$

12) $y = \sqrt{\frac{3 - x}{1 - x}}$