\[ \begin{split} &\lim_{x \to 2}\left(\frac{1}{x-2}-\frac{4}{x^2-4}\right)=\\[16pt] &=\lim_{x \to 2}\left(\frac{x+2}{(x-2)(x+2)}-\frac{4}{(x-2)(x+2)}\right)=\\[16pt] &=\lim_{x \to 2}\frac{(x-2)}{(x-2)(x+2)}=\\[16pt] &=\lim_{x \to 2}\frac{1}{x+2}=\frac{1}{4} \end{split} \]