阅读下列题目的计算过程:(x-3)/(x²-1)-2/(1+x)=(x-3)/(x+1)(x-1)-2(x-1)/(x+1)(x-1)(A)=x-3-2(x-1)(B)=x-3-2x+2(C)=-x-1(D)(1)上述计算过程,从哪一步开始出现错误请写出其代号:(2)错误的原因:(3)本题的正确结果为:

问题描述:

阅读下列题目的计算过程:
(x-3)/(x²-1)-2/(1+x)
=(x-3)/(x+1)(x-1)-2(x-1)/(x+1)(x-1)(A)
=x-3-2(x-1)(B)
=x-3-2x+2(C)
=-x-1(D)
(1)上述计算过程,从哪一步开始出现错误请写出其代号:
(2)错误的原因:
(3)本题的正确结果为:

B 丢掉了分母(x-3)/(x²-1)-2/(1+x)=(x-3)/(x+1)(x-1)-2(x-1)/(x+1)(x-1)(A)=[x-3-2(x-1)] /(x+1)(x-1) (B)=(x-3-2x+2)//(x+1)(x-1) (C)=(-x-1)/(x+1)(x-1) (D)=-(x+1)/(x+1)(x-1) ...