Chapter 7 - Rational Functions - 7.3 Multiplying and Dividing Rational Expressions - 7.3 Exercises - Page 581: 43

$= \frac{(a-5)}{(a+4)}$

$\frac{a^{2}-25}{a^{2}+6a+5} \times \frac{a^{2}-1}{a^{2}+3a-4}$ $= \frac{(a-5)(a+5)}{(a+5)(a+1)} \times \frac{(a-1)(a+1)}{(a+4)(a-1)}$ $= \frac{(a-5)(a+5)}{(a+5)(a+1)} \times \frac{(a+1)}{(a+4)}$ $= \frac{(a-5)}{(a+1)} \times \frac{(a+1)}{(a+4)}$ $= \frac{(a-5)}{1} \times \frac{1}{(a+4)}$ $= \frac{(a-5)}{(a+4)}$