(x+3)(x+7)+1≤(2x-3)²-8(x-5)​

(x+3)(x+7) + 1 ≤ (2x-3)² - 8(x-5)

x² + 10x + 21 + 1 ≤ 4x² - 12x + 9 - 8x + 40

x² + 10x + 22 ≤ 4x² - 20x + 49

0 ≤ 3x² - 30x + 27

3x² - 30x + 27 ≥ 0

x² - 10x + 9 ≥ 0

(x - 1)(x - 9) ≥ 0

x ≤ 1 или x ≥ 9

(-∞, 1]∪[9, +∞).