Verified answer

(ac - ab)/(b² - c²) = a(c - b) / (b - c)(b +c) = - a/(b + c)  (на c - b)

(b² + ab)/(3a² - 3ab) = b(a + b) / 3a(a - b) нет

(x² - xy)/(9x² - 18xy + 9y²) = x(x - y)/9(x - y)² = x/9(x - y) ( на x - y)

(a^4 - a)/(3a² + 3a + 3) = a(a³ - 1) / (3a² + 3a + 3) = a(a-1)(a² + a + 1)/3(a² + a + 1) = a(a - 1)/3 (на a² + a + 1)

(x³ - 1)/(x² - 1) = (x - 1)(x² + x + 1) /(x - 1)(x + 1) = (x² + x + 1)/(x + 1) (на x - 1)