1. The problem asks: For the function $f(x) = -5$, where is it negative? 2. Since $f(x) = -5$ is a constant function always equal to $-5$, it is negative for all real numbers. 3. Therefore, the function is negative on the interval $$]-\infty, \infty[$$. Final answer: (c) $$]-\infty, \infty[$$