Решение:
\( -4x^2 + 16x + 9 = 0 \)
Здесь \( a = -4 \), \( b = 16 \), \( c = 9 \).
\[ D = 16^2 - 4 \times (-4) \times 9 \]
\[ D = 256 - (-16) \times 9 \]
\[ D = 256 + 144 \]
\[ D = 400 \]
\[ x_1 = \frac{-16 + \sqrt{400}}{2 \times (-4)} \]
\[ x_1 = \frac{-16 + 20}{-8} \]
\[ x_1 = \frac{4}{-8} = -0.5 \]
\[ x_2 = \frac{-16 - \sqrt{400}}{2 \times (-4)} \]
\[ x_2 = \frac{-16 - 20}{-8} \]
\[ x_2 = \frac{-36}{-8} = 4.5 \]
Ответ: \( -0.5 \), \( 4.5 \)