Simplify (4- square root of x+15)/(1-x^2)

$\frac{4 - \sqrt{x + 15}}{1 - x^{2}}$

Rewrite $1$ as $1^{2}$ .

$\frac{4 - \sqrt{x + 15}}{1^{2} - x^{2}}$

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = 1$ and $b = x$ .

$\frac{4 - \sqrt{x + 15}}{(1 + x) (1 - x)}$