\[y = \sqrt{5x - 4x^{2}}\]
\[5x - 4x^{2} \geq 0\]
\[4x^{2} - 5x \leq 0\]
\[x(4x - 5) \leq 0\]
\[4x(x - 1,25) \leq 0\]
\[Ответ:x \in \lbrack 0;1,25\rbrack.\]