(a-3)/(a^2-1)-2/(a+1)=(a-3)/(a+1)(a-1)-2(a-1)/(a+1)(a-1)=a-3-2(a-1)=a-3-2a+2=-a-1.(1)上述计算过程中,从哪一步开始出现错误的?(2)错误的原因是______________;(3)请你给出正确的解答.

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(a-3)/(a^2-1)-2/(a+1)=(a-3)/(a+1)(a-1)-2(a-1)/(a+1)(a-1)=a-3-2(a-1)=a-3-2a+2=-a-1.(1)上述计算过程中,从哪一步开始出现错误的?(2)错误的原因是______________;(3)请你给出正确的解答.

(a-3)/(a^2-1)-2/(a+1)=(a-3)/(a+1)(a-1)-2(a-1)/(a+1)(a-1)=a-3-2(a-1)=a-3-2a+2=-a-1.(1)上述计算过程中,从哪一步开始出现错误的?(2)错误的原因是______________;(3)请你给出正确的解答.
(a-3)/(a^2-1)-2/(a+1)=(a-3)/(a+1)(a-1)-2(a-1)/(a+1)(a-1)=a-3-2(a-1)=a-3-2a+2=-a-1.
(1)上述计算过程中,从哪一步开始出现错误的?
(2)错误的原因是______________;
(3)请你给出正确的解答.

(a-3)/(a^2-1)-2/(a+1)=(a-3)/(a+1)(a-1)-2(a-1)/(a+1)(a-1)=a-3-2(a-1)=a-3-2a+2=-a-1.(1)上述计算过程中,从哪一步开始出现错误的?(2)错误的原因是______________;(3)请你给出正确的解答.
(1)第二个等号后
(2)把分母忘记了
(3)
(a-3)/(a^2-1)-2/(a+1)=(a-3)/(a+1)(a-1)-2(a-1)/(a+1)(a-1)=[a-3-2(a-1)]/(a+1)(a-1)=(a-3-2a+2)/(a+1)(a-1)=(-a-1)/(a+1)(a-1)=-1/(a-1)希望能帮助你~

=a-3-2(a-1)出现错误
错去原因是把分母丢了
原式==(a-3)/(a+1)(a-1)-2(a-1)/(a+1)(a-1)
=[(a-3)-2(a-1)]/[(a+1)(a-1)]
=(a-3-2a+2)/[(a+1)(a-1)]
=-(a+1)/[(a+1)(a-1)=-1/(a-1)=1/(1-a)