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原式=[-(a²-3)/(a+1)²+(a-a-1)/(a+1)]÷(a-1+1)/(a-1)
=[-(a²-3)/(a+1)²-1/(a+1)]÷a/(a-1)
=-(a²-3+a+1)/(a+1)²×(a-1)/a
=-(a+2)(a-1)/(a+1)²×(a-1)/a
=-(a+2)(a-1)²/a(a+1)²
1年前
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http://zhidao.baidu.com/question/384023649.html?quesup2&oldq=1