Решение:
(5x-1)(x+2) = 5x^2 + 10x - x - 2 = 5x^2 + 9x - 23(x-4)(x+4) = 3(x^2 - 16) = 3x^2 - 482(2x+3)² = 2(4x² + 12x + 9) = 8x² + 24x + 18(5x^2 + 9x - 2) + (3x^2 - 48) = (8x² + 24x + 18) - 8
5x^2 + 9x - 2 + 3x^2 - 48 = 8x² + 24x + 18 - 8
8x^2 + 9x - 50 = 8x² + 24x + 10
8x^2 + 9x - 50 - 8x² - 24x - 10 = 0
(8x² - 8x²) + (9x - 24x) + (-50 - 10) = 0
-15x - 60 = 0
-15x = 60
x = 60 / (-15)
x = -4
Ответ: -4