а) a² - 6a = a(a - 6)
б) x² - 49 = x² - 7² = (x - 7)(x + 7)
в) y² + 6y + 9 = y² + 2 * 3 * y + 3² = (y + 3)²
г) 2a - 2b + ca - cb = 2(a - b) + c(a - b) = (a - b)(2 + c)