(x² - 16)/(3 - √(x + 5)) = (x² - 16)(3 + √(x + 5))/(3 - √(x + 5))(3 + √(x + 5))=
(x - 4)(x + 4)(3 + √(x + 5))/(9 - (x + 5)) = (x - 4)(x + 4)(3 + √(x + 5))/(9 - (x + 5)) = (x - 4)(x + 4)(3 + √(x + 5))/(4 - x) = - (x + 4)(3 + √(x + 5))
a² - b² = (a - b)(a + b)
