(UNB) A expressão $\phantom{X}\dfrac{\;3a\,-\,4\;}{a^2\,-\,16}\,-\,\dfrac{1}{\;a\,-\,4\;}\phantom{X}$($\;{\small a\,\neq\,4}\;$) é equivalente a:
a)
$\,\dfrac{1}{\;a\,-\,4\;}\,$
b)
$\,\dfrac{2}{\;a\,+\,4\;}\,$
c)
$\,\dfrac{2}{\;a\,-\,4\;}\,$
d)
$\,\dfrac{\;a\,+\,4\;}{\;a\,-\,4\;}\,$
