(x-y)(y-z)(z-x)/((z-y)(y-x)(x-z))=(x-y)(y-z)(z-x)/(-(y-z)(x-y)(z-x))=-1(y-x)/(x²-y²)=-(x-y)/(x+y)(x-y)=-1/(x+y)(m+2n)/(m²-4n²)=(m+2n)/((m+2n)(m-2n))=)1/(m-2n)把m=1,n=3代入得：1/(1-...第2题你看看是不是错了，我们的明天要对答案了没看错呀，你觉得哪儿有问题？