To solve for $f(-4)$ when $f(x) = -x - 1$:

1. Substitute $-4$ into the given function: $f(-4) = -(-4) - 1$

2. Simplify the expression: $f(-4) = 4 - 1$

3. Final result: $f(-4) = 3$

So, $f(-4) = 3$.

Do you want further details or have any questions? Here are five related questions to deepen your understanding:

1. What happens to the function $f(x)$ if $x = 0$?
2. How do you determine if $f(x) = -x - 1$ is linear?
3. What is the slope and y-intercept of the function $f(x) = -x - 1$?
4. Can we determine $f(a)$ for any general value $a$? How?
5. What would $f(x)$ look like if $x$ were replaced by $2x$?

Tip: Substitution is a fundamental concept in mathematics; always replace the variable with the value you're evaluating, and simplify step by step.