4. Решите уравнение: $$(5x - 1)(x + 2) + 3(x - 4)(x + 4) = 2(2x + 3)^2 - 8$$.

$$(5x - 1)(x + 2) + 3(x - 4)(x + 4) = 2(2x + 3)^2 - 8$$ $$5x^2 + 10x - x - 2 + 3(x^2 - 16) = 2(4x^2 + 12x + 9) - 8$$ $$5x^2 + 9x - 2 + 3x^2 - 48 = 8x^2 + 24x + 18 - 8$$ $$8x^2 + 9x - 50 = 8x^2 + 24x + 10$$ $$8x^2 - 8x^2 + 9x - 24x = 10 + 50$$ $$-15x = 60$$ $$x = \frac{60}{-15}$$ $$x = -4$$ **Ответ:** $$x = -4$$