(3a^2-2a-5)/(3a^2-2a-1)*(a^2-1)/(a+1)÷(a+1)=(a+1)(3a-5)/(a-1)(3a+1) * (a+1)(a-1)/(a+1) * 1/(a+1)=(a+1)(3a-5)(a+1)(a-1)/(a-1)(3a+1)(a+1)(a+1)=(3a-5)/(3a+1) 你看一下分子分母是不是这样,有不懂再追问...第一步那个分式怎么化简的，有点不懂3a^2-2a-5=(a+1)(3a-5)3a^2-2a-1=(a-1)(3a+1) 因式分解