Evaluate the following function for the given value. \[ \begin{array}{l} f(x)=-\sqrt{-9 x-7} \\ f(-26)=? \end{array} \] Round your answer to two decimal places.

Step 1 ：The function is given as \(f(x)=-\sqrt{-9x-7}\). We are asked to find the value of the function at \(x=-26\). To do this, we substitute \(x=-26\) into the function and calculate the result.

Step 2 ：Substitute \(x=-26\) into the function: \(f(-26)=-\sqrt{-9(-26)-7}\).

Step 3 ：Simplify the expression inside the square root: \(f(-26)=-\sqrt{227}\).

Step 4 ：Calculate the square root: \(f(-26)=-15.066519173319364\).

Step 5 ：Round the result to two decimal places: \(f(-26)=-15.07\).

Step 6 ：Final Answer: The value of the function \(f(x)=-\sqrt{-9x-7}\) at \(x=-26\) is approximately \(\boxed{-15.07}\).