\[\boxed{\text{99.\ }\text{ОК\ ГДЗ\ -\ домашка\ на\ 5}}\]
\[\textbf{а)}\ y = x^{2} + 3x - 25\]
\[D(y) = ( - \infty; + \infty).\]
\[\textbf{б)}\ y = \sqrt{5 - 3x}\]
\[5 - 3x \geq 0\]
\[3x \leq 5\]
\[x \leq 0,6.\]
\[D(y) = ( - \infty;0,6\rbrack.\]
\[\textbf{в)}\ \ y = \frac{x^{2} - 1}{x + 1}\]
\[x + 1 \neq 0\]
\[x \neq - 1.\]
\[D(y) = ( - \infty; - 1) \cup ( - 1; + \infty).\]
\[\textbf{г)}\ y = \frac{x + 1}{x^{2} + 1}\]
\[x^{2} + 1 \neq 0\]
\[x^{2} \neq - 1\]
\[x - любое\ число.\ \]
\[D(y) = ( - \infty; + \infty).\]