\[(7y + 3)^{2} \leq (7y)^{2} + 9^{2}\]
\[49y^{2} + 9 + 42y \leq 49y^{2} + 81\]
\[42y \leq 81 - 9\]
\[42y \leq 72\]
\[y \leq \frac{12}{7}\]
\[y \leq 1\frac{5}{7}\]
\[y = 1 \Longrightarrow наибольшее\ \]
\[целое\ число\]
\[Ответ:y \in \left( - \infty;1\frac{5}{7} \right);\ \ y = 1.\]