а) 2(m + 3)-m(m+3) = (2 - m)(m + 3)

б) x⁴+3x³-3x²-9x = x(x³ + 3x² - 3x - 9) = x(x²(x + 3) - 3(x + 3)) = x(x² - 3)(x + 3)