To simplify the denominator of the expression given, we need to focus on the term \(-(-3)^2\).
First, calculate \((-3)^2\): \[ (-3)^2 = 9 \] Now, we negate this result: \[ -9 \]
Therefore, the simplified denominator is: \[ -(-3)^2 = -9 \]
So, the simplified denominator is \(-9\).