1) (a - b)³ - 3(a - b)² = (a - b)² * (a - b) - 3(a - b)² = (a - b)² * (a - b - 3)
2) (x + y)³ + 2x(x + y)² = (x + y)² * (x + y) + 2x(x + y)² = (x + y)² (3x + y)
3) (m + n)³ - m² - 2mn - n² = (m + n)³ - (m + n)² = (m + n)² * (m +n) - (m + n)² = (m + n)² (m + n -1)
4) x² - 4xy + 4y² - (x - 2y)² = (x - 2y)² - (x - 2y)² = 0