Answer
$\frac{x-5}{x+4}$ and $x\ne-1$.
Work Step by Step
$\frac{x^2-4x-5}{x^2+5x+4}=\frac{x^2+x-5x-5}{x^2+x+4x+4}=\frac{x(x+1)-5(x+1)}{x(x+1)+4(x+1)}=\frac{(x+1)(x-5)}{(x+1)(x+4)}=\frac{x-5}{x+4}$ and $x\ne-1$.
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