\[\left( a^{2} + 6 \right)(3a - 7) \geq 0\]
\[a^{2} + 6 > 0\ при\ любом\ a;\ \]
\[3a - 7 \geq 0\]
\[3a \geq 7\]
\[a \geq \frac{7}{3}\]
\[a \geq 2\frac{1}{3}.\]
\[Ответ:при\ a \geq 2\frac{1}{3}.\]