\[f(x) = \frac{5}{3 - x}\]
\[3 - x \neq 0\]
\[x \neq 3.\]
\[f(x) = 1:\]
\[1 = \frac{5}{3 - x}\]
\[3 - x = 5\]
\[x = 3 - 5\]
\[x = - 2\ (существует).\]