Решим уравнение:
$$2x^2 + 4x - 4 = x^2 + 5x + (-3 + x^2)$$ $$2x^2 + 4x - 4 = x^2 + 5x - 3 + x^2$$ $$2x^2 + 4x - 4 = 2x^2 + 5x - 3$$ $$2x^2 - 2x^2 + 4x - 5x = -3 + 4$$ $$-x = 1$$ $$x = -1$$
Ответ: -1