6) Simplify \( \frac{y^2-12y+36}{36-y^2} \).

\( \frac{y^2-12y+36}{36-y^2} = \frac{(y-6)^2}{(6-y)(6+y)} = \frac{(y-6)^2}{-(y-6)(y+6)} = \frac{-(y-6)}{y+6} \), provided \( y
eq 6 \) and \( y
eq -6 \).