\[4 \cdot (a + 1)x² + (a - 3)x - 1 = 0\]
\[= a^{2} - 6a + 9 + 16a + 16 =\]
\[= a^{2} + 10a + 25 = (a + 5)^{2}\]
\[При\ D = 0:\]
\[(a + 5)^{2} = 0\]
\[a + 5 = 0\]
\[a = - 5.\]
\[1)\ a = - 5:\]
\[x = \frac{3 - ( - 5) \pm | - 5 + 5|}{8 \cdot ( - 5 + 1)} =\]
\[3)\ \ a > - 5:\]
\[x_{1} = \frac{3 - a + a + 5}{8 \cdot (a + 1)} =\]
\[x_{2} = \frac{3 - a - a - 5}{8 \cdot (a + 1)} =\]
\[= \frac{- 2a - 2}{8 \cdot (a + 1)} =\]
\[Ответ:\ a = - 5 \Longrightarrow \ x = - \frac{1}{4};\ \]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ a > - 5 \Longrightarrow \ x_{1} = \frac{1}{a + 1};\ \ \ \]
\[x_{2} = - \frac{1}{4}.\]