Решение:
\[ -8x^2 + 6x + 9 = 0 \]
\[ D = b^2 - 4ac \]
Где a = -8, b = 6, c = 9.
\[ D = 6^2 - 4(-8)(9) = 36 + 288 = 324 \]
\[ x = \frac{-b \pm \sqrt{D}}{2a} \]
\[ x_1 = \frac{-6 + \sqrt{324}}{2(-8)} = \frac{-6 + 18}{-16} = \frac{12}{-16} = -0,75 \]
\[ x_2 = \frac{-6 - \sqrt{324}}{2(-8)} = \frac{-6 - 18}{-16} = \frac{-24}{-16} = 1,5 \]
Ответ: -0,75; 1,5