#### Answer

$\frac{5x}{x-5}$

#### Work Step by Step

To factor the denominator, we use the rule $a^{2}-b^{2}=(a+b)(a-b)$. Then, we factor the expression in the numerator in order to cancel out common factors in the numerator and the denominator:
$\frac{5x^{2}+25x}{x^{2}-25}$
=$\frac{5x(x+5)}{x^{2}-5^{2}}$
=$\frac{5x(x+5)}{(x+5)(x-5)}$
=$\frac{5x}{x-5}$