\[5 \cdot \left( 3x^{2} + x \right) - 4 \cdot (2 - 7x) =\]
\[= 2 \cdot \left( 3x^{2} + 17 \right)\]
\[15x^{2} + 5x - 8 + 28x =\]
\[= 6x^{2} + 34\]
\[9x² + 33x - 42 = 0\ \ \ \ |\ :3\]
\[3x^{2} + 11x - 14 = 0\]
\[D = b^{2} - 4ac =\]
\[= 121 - 4 \cdot 3 \cdot ( - 14) =\]
\[= 121 + 168 = 289\]
\[x_{1} = \frac{- 11 + 17}{6} = \frac{6}{6} = 1\]
\[x_{2} = \frac{- 11 - 17}{6} = - \frac{28}{6} =\]
\[= - \frac{14}{3} = - 4\frac{2}{3}\]
\[Ответ:x = 1\ \ и\ \ \ x = - 4\frac{2}{3}.\]