\[a² - 11a + 2,8 = 0\]
\[D = b^{2} - 4ac =\]
\[= 121 - 4 \cdot 1 \cdot 2,8 =\]
\[= 121 - 11,2 = 109,8\]
\[a_{1} = \frac{11 + \sqrt{109,8}}{2}\]
\[a_{2} = \frac{11 - \sqrt{109,8}}{2}\]
\[Ответ:\ \ a_{1} = \frac{11 + \sqrt{109,8}}{2};\ \ \ \]
\[a_{2} = \frac{11 - \sqrt{109,8}}{2}.\]