The function $g(x)$ is the reflection of $f(x) = -x + 4$ across the x-axis. To reflect a function across the x-axis, you multiply the entire function by $-1$.

Given: $f(x) = -x + 4$

The reflection across the x-axis is: $g(x) = -f(x) = -(-x + 4)$

Simplify: $g(x) = x - 4$

Thus, the reflected function is: $g(x) = x - 4$

Do you want details or have any questions?

Here are 5 related questions to expand your understanding:

1. How do you reflect a function across the y-axis?
2. What is the effect of reflecting the function $f(x) = x^2$ across the x-axis?
3. How do you reflect a function across the line $y = x$?
4. What happens if you reflect a function across both the x-axis and y-axis?
5. Can a function ever be identical to its reflection across the x-axis?

Tip: Reflecting a function across the x-axis simply changes the sign of the output of the function, but keeps the inputs the same.