\[\frac{3x + 1}{4} - \frac{7x - x^{2}}{10} = \frac{x^{2} - 1}{8}\ \ \ \ \ \ | \cdot 40\ \]
\[10 \cdot (3x + 1) - 4 \cdot \left( 7x - x^{2} \right) =\]
\[= 5 \cdot (x² - 1)\]
\[30x + 10 - 28x + 4x^{2} - 5x^{2} + 5 = 0\]
\[- x^{2} + 2x + 15 = 0\]
\[x^{2} - 2x - 15 = 0\]
\[x_{1} + x_{2} = 2\]
\[x_{1} \cdot x_{2} = - 15 \Longrightarrow x_{1} = - 3\ \ \ и\ \ \]
\[\ x_{2} = 5\]
\[Ответ:x = - 3\ \ и\ \ x = 5.\]