г) $$ \frac{2}{m-4} - \frac{5m-4}{m^2-16} = \frac{2}{m-4} - \frac{5m-4}{(m-4)(m+4)} = \frac{2(m+4) - (5m-4)}{(m-4)(m+4)} = \frac{2m+8 - 5m+4}{(m-4)(m+4)} = \frac{-3m+12}{(m-4)(m+4)} = \frac{-3(m-4)}{(m-4)(m+4)} = \frac{-3}{m+4} $$
Ответ: $$ \frac{-3}{m+4} $$