\[\boxed{\text{75.\ }\text{ОК\ ГДЗ\ -\ домашка\ на\ 5}}\]
\[\textbf{а)}\ 5\sqrt{x} = 1\]
\[\sqrt{x} = \frac{1}{5}\]
\[x = \frac{1}{25} = 0,04.\]
\[Ответ:\ x = 0,04.\]
\[\textbf{б)}\ \sqrt{x - 4} = 15\]
\[x - 4 = 225\]
\[x = 229.\]
\[Ответ:x = 229.\]