\[1)\ f(x) = \frac{x^{2}}{|x|} = |x|;\ \ \ a = 0:\]
\[x \neq 0.\]
\[Ответ:\ \ 0.\]
\[2)\ f(x) = \frac{x^{2} - 9}{x + 3};\ \ \ a = - 3:\]
\[f(x) = \frac{(x - 3)(x + 3)}{x + 3} = x - 3;\]
\[x + 3 \neq 0\]
\[x \neq - 3.\]
\[Ответ:\ - 6.\]
\[3)\ f(x) = \frac{x^{3} - 1}{x - 1};\ \ a = 1:\]
\[f(x) = \frac{(x - 1)\left( x^{2} + x + 1 \right)}{x - 1} =\]
\[= x^{2} + x + 1;\]
\[x - 1 \neq 0\]
\[x \neq 1.\]
\[Ответ:\ \ 3.\]
\[4)\ f(x) = \frac{2x^{2} - x - 6}{x - 2};\ \ \ a = 2:\]
\[f(x) = \frac{(2x + 3)(x - 2)}{x - 2} = 2x + 3;\]
\[x - 2 \neq 0\]
\[x \neq 2.\]
\[Ответ:\ \ 7.\]