x³ - 8y³ - x² - 2xy - 4y²
= (x³ - 8y³) - (x² + 2xy + 4y²)
= (x - 2y)(x² +2xy + 4y²) - (x² + 2xy + 4y²)
= (x - 2y - 1)(x² + 2xy + 4y²)