\[\left( \sqrt{16x^{2} + 24x + 9} \right)^{2} = (5)^{2}\]
\[16x^{2} + 24x + 9 = 25\]
\[16x² + 24x - 16 = 0\ \ \ \ \ |\ :8\]
\[2x² + 3x - 2 = 0\]
\[D = 9 + 16 = 25\]
\[x_{1,2} = \frac{- 3 \pm 5}{4} = \frac{1}{2};\ - 2.\]
\[Ответ:\ - 2;\ \frac{1}{2}.\]