\[\ x² + 17 \geq 2 \cdot (5x - 4)\]
\[x^{2} + 17 \geq 10x - 8\]
\[x^{2} - 10x + 25 \geq 0\]
\[(x - 5)^{2} \geq 0 \Longrightarrow ч.т.д.\]
\[a < c\]
\[\ 7,2a < 7,2c\]