\[\boxed{\text{1074.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[\textbf{а)}\ y = \frac{x^{2} - 9}{6 + 2x} =\]
\[= \frac{(x - 3)(x + 3)}{2 \cdot (x + 3)} = \frac{x - 3}{2} =\]
\[= 0,5x - 1,5.\]
\[ОДЗ:\]
\[6 + 2x \neq 0\]
\[2x \neq - 6\]
\[x \neq - 3.\]
\[\textbf{б)}\ y = \frac{4 - x^{2}}{x^{2} + 2x} =\]
\[= \frac{(2 - x)(2 + x)}{x(x + 2)} =\]
\[= \frac{2 - x}{x} = \frac{2}{x} - 1.\]
\[ОДЗ:\]
\[x^{2} + 2x \neq 0\]
\[x(x + 2) \neq 0\]
\[x \neq 0;\ \ x \neq - 2.\]