(a-1)/[(a+1)²-4]与(1-a)/(2-4a+2a²)是这个??先化简:(a-1)/[(a+1)²-4]=(a-1)/[(a+1-2)(a+1+2)]=1/(a+3)(1-a)/(2-4a+2a²)=(1-a)/[2(1-2a+a²)]=(1-a)/[2(a-1)²]=1/[2(a-1)]再通分:1/(a+3)=2(a-1)/[2(a-1)(a+3)]1/[2(a-1)]=(a+3)/[2(a-1)(a+3)]