#### Answer

$\frac{y+4}{y-5}$

#### Work Step by Step

To simplify, divide both the numerator and denominator by their greatest common factor.
Use factorization to find the GCF.
$\frac{y^2+5y+4}{y^2-4y-5}=\frac{(y+4)(y+1)}{(y-5)(y+1)}=\frac{(y+4)(y+1)\div(y+1)}{(y-5)(y+1)\div(y+1)}=\frac{y+4}{y-5}$