a² - 6a + 9 = (a - 3)² = (a - 3)(a - 3)
9x² - 1 = (3x)² - 1² = (3x - 1)(3x + 1)
3ab² - 6a²b = 3ab(b - 2a)
a² - 6a + 9 = (a - 3)² = (a - 3)(a - 3)
9x² - 1 = (3x)² - 1² = (3x - 1)(3x + 1)
3ab² - 6a²b = 3ab(b - 2a)