\(\lim\limits_{x\rightarrow2^-}\left(\dfrac{1}{x-2}-\dfrac{1}{x^2-4}\right)\)
\(=\lim\limits_{x\rightarrow2^-}\dfrac{x+2-1}{\left(x-2\right)\left(x+2\right)}\)
\(=\lim\limits_{x\rightarrow2^-}\dfrac{x+1}{\left(x-2\right)\left(x+2\right)}\)
\(=-\infty\) vì \(\left\{{}\begin{matrix}\lim\limits_{x\rightarrow2^-}\dfrac{x+1}{x+2}=\dfrac{2+1}{2+2}=\dfrac{3}{4}>0\\x-2< 0\end{matrix}\right.\)