б) $$-x^2 - 10x - 25 = -(x^2 + 10x + 25) = -(x + 5)^2 = -(x + 5)(x + 5)$$.
в) $$a^4b^2 - b^4a^2 = a^2b^2(a^2 - b^2) = a^2b^2(a - b)(a + b)$$.