To find the sum of the rational expressions \(-\frac{4}{x-4} + \frac{x^2 - 2}{2x - 8}\), we first need to rewrite the second expression.
Notice that \(2x - 8\) can be factored:
\[ 2x - 8 = 2(x - 4) \]
So, we can rewrite the second term:
\[ \frac{x^2 - 2}{2x - 8} = \frac{x^2 - 2}{2(x - 4)} = \frac{1}{2} \cdot \frac{x^2 - 2}{x - 4} \]
Now we can express the first term with a common denominator:
\[ -\frac{4}{x-4} = -\frac{4}{1} \cdot \frac{2}{2} \cdot \frac{1}{x-4} = -\frac{8}{2(x-4)} \]
Now we have:
\[ -\frac{8}{2(x - 4)} + \frac{x^2 - 2}{2(x - 4)} = \frac{-8 + (x^2 - 2)}{2(x - 4)} \]
Combine the numerators:
\[ = \frac{x^2 - 10}{2(x - 4)} \]
Thus, the sum of the rational expressions is:
\[ \frac{x^2 - 10}{2(x - 4)} \]
Now that we have added the rational expressions and simplified them, we can conclude that the final answer is:
\[ \frac{x^2 - 10}{2(x - 4)} \]
In simplest form, the answer is:
\[ \boxed{\frac{x^2 - 10}{2(x - 4)}} \]