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你后面括号中的计算错了,应该是这样的:
原式=x/(x+1)(x-1)÷[(x-1)/(x-1)-x/(x-1)] (后面括号中的通分过程我详细写出来了)
=x/(x+1)(x-1)÷[(x-1-x)/(x-1)] (后面括号中分子相减,分母不变)
=x/(x+1)(x-1)÷[-1/(x-1)]
=x/(x+1)(x-1)×[-(x-1)]
=-x/(x+1)
把x=-2 代入得:-x/(x+1)=-(-2)/(-2+1)=-2
原式=x/(x+1)(x-1)÷[(x-1)/(x-1)-x/(x-1)] (后面括号中的通分过程我详细写出来了)
=x/(x+1)(x-1)÷[(x-1-x)/(x-1)] (后面括号中分子相减,分母不变)
=x/(x+1)(x-1)÷[-1/(x-1)]
=x/(x+1)(x-1)×[-(x-1)]
=-x/(x+1)
把x=-2 代入得:-x/(x+1)=-(-2)/(-2+1)=-2
来自:求助得到的回答
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