\[Уравнение\ имеет\ \]
\[единственный\ корень\ \]
\[при\ D = 0.\]
\[cx² - 5x + 2 = 0\]
\[D = ( - 5)^{2} - 4 \cdot c \cdot 2 = 25 - 8c\]
\[25 - 8c = 0\]
\[8c = 25\]
\[c = \frac{25}{8} = 3\frac{1}{8}\]
\[Ответ:\ \ при\ c = 0;\ c = 3\frac{1}{8}.\]