\[\ b^{2} + 10 \geq 2 \cdot (4b - 3)\]
\[b^{2} + 10 \geq 8b - 6\]
\[b^{2} - 8b + 16 \geq 0\]
\[(b - 4)^{2} \geq 0 \Longrightarrow \ \ ч.т.д.\]
\[a < b\]
\[\ 15a < 15b\]