\[\left( a^{2} + 10 \right)(2a - 5) \geq 0\]
\[a^{2} + 10 > 0\ при\ любом\ a;\]
\[2a - 5 \geq 0\]
\[2a \geq 5\]
\[a \geq 2,5.\]
\[Ответ:при\ a \geq 2,5.\]