\[\sqrt{- 0,85 \cdot (4,2a - 12,6)}\]
\[- 0,85 \cdot (4,2a - 12,6) \geq 0\]
\[4,2a - 12,6 \leq 0\]
\[4,2a \leq 12,6\]
\[a \leq 3.\]
\[Ответ:2)\ ( - \infty;3\rbrack.\]