\[y = x\left( 1 - \sqrt{5} \right);\ \ \ \ \]
\[\lbrack 2\sqrt{5} - 2;4\sqrt{5} - 4\rbrack\]
\[2\sqrt{5} - 2 \leq x\left( 1 - \sqrt{5} \right) \leq 4\sqrt{5} - 4\]
\[- 4 \leq x \leq - 2\]
\[Ответ:\ \lbrack - 4; - 2\rbrack.\]