To find $(f + g)(x)$, we need to add the two functions $f(x)$ and $g(x)$. The given functions are:

$f(x) = -3x$ $g(x) = -4x + 4$

Now, add them together:

$(f + g)(x) = f(x) + g(x) = (-3x) + (-4x + 4)$

Simplify:

$(f + g)(x) = -3x - 4x + 4 = -7x + 4$

Thus, $(f + g)(x) = -7x + 4$.

Would you like more details or have any questions?

Here are some related questions:

1. What is $(f - g)(x)$ for the same functions $f(x)$ and $g(x)$?
2. What is $(f \cdot g)(x)$ for the same functions?
3. What is $(f / g)(x)$ for these functions?
4. How do you find the domain of $(f + g)(x)$?
5. How does changing the values of $f(x)$ and $g(x)$ affect the result of $(f + g)(x)$?

Tip: When combining functions, always pay attention to both the coefficients of the variables and any constants.