5xy² - 45x - 8y² + 72 = (5xy² - 45x) - (8y² - 72) = 5x(y² - 9) - 8(y² - 9) ==(y² - 9)(5x - 8) = (y - 3)(y + 3)(5x - 8)
16 - 9a² - 72ab - 144b² = 16 - (9a² + 72ab + 144b²) = 16 - (3a + 12b)² == 4² - (3a + 12b)² = (4 - 3a - 12b)(4 + 3a + 12b)
ac³ + c³ - 27a - 27 = (ac³ + c³) - (27a + 27) = c³(a + 1) - 27(a + 1) = = (a + 1)(c³ - 27) = (a + 1)(c - 3)(c² +3c + 9)
32 + 243x⁵ = 2⁵ + (3x)⁵ = (3x + 2)(81x⁴ - 54x³ + 36x² - 24x + 16)