Ответ: x = 2
(2x-7)(x+1)+3(4x-1)(4x + 1) = 2(5x-2)² - 53
2x² + 2x - 7x - 7 + 3(16x² - 1) = 2(25x² - 20x + 4) - 53
2x² - 5x - 7 + 48x² - 3 = 50x² - 40x + 8 - 53
50x² - 5x - 10 = 50x² - 40x - 45
35x = -35
x = -1
Ответ: x = -1