a) (y - 6)² - 9y²
= (y - 6 - 3y)(y - 6 + 3y)
= (-2y - 6)(4y - 6)
= -2(y + 3) * 2(2y - 3)
= -4(y + 3)(2y - 3)
б) c² - d² - c + d
= (c - d)(c + d) - (c - d)
= (c - d)(c + d - 1)
= (c - d)(c + d - 1)
в) x⁹ + 27
= (x³)^3 + 3^3
= (x³ + 3)(x⁶ - 3x³ + 9)
= (x³ + 3)(x⁶ - 3x³ + 9)