解
(a-1)/(a²+2a+1)=(a-1)/(a+1)²
6/(a²-1)=6/(a-1)(a+1)
∴最简公分母为(a-1)(a+1)²
(a-1)/(a²+2a+1)=(a-1)/(a+1)²=(a-1)²/(a-1)(a+1)²
6/(a²-1)=6/(a-1)(a+1)=6(a+1)/(a-1)(a+1)²