Решите задачу:
(4a²-3a+5)/(a-1)(a²+a+1) -(1-2a)/(a²+a+1)-6/(a-1)= =(4a²-3a+5-a+1+2a²-2a-6a²-6a-6)/(a³-1)=-12a/(a³-1)=12a/(1-a³)