a) $$ \frac{3c}{(c-2)^2} - \frac{6}{c-2} = \frac{3c - 6(c-2)}{(c-2)^2} = \frac{3c - 6c + 12}{(c-2)^2} = \frac{-3c + 12}{(c-2)^2} = \frac{-3(c-4)}{(c-2)^2} $$
Ответ: $$ \frac{-3(c-4)}{(c-2)^2} $$