\[\ b² + 5 \geq 10 \cdot (b - 2)\]
\[b^{2} + 5 \geq 10b - 20\]
\[b^{2} - 10b + 25 \geq 0\]
\[(b + 5)^{2} \geq 0 \Longrightarrow ч.т.д.\ \]
\[a > b\]
\[\ 18a > 18b\]