x的平方-2xy-3y的平方分之x的平方+xy×x - 知识问答

x的平方-2xy-3y的平方分之x的平方+xy×x-y分之3y-x+(x的-1次方+y的-1次方)÷(x的-1次方-y的

2个回答

(x^2+xy)/(x^2-2xy-3y^2)×(3y-x)/(x-y)+[x^(-1)+y^(-1)]÷[x^(-1)-y^(-1)]
=x(x+y)/[(x+y)(x-3y)]×[-(x-3y)/(x-y)]+[1/x+1/y]÷[1/x-1/y]
=-x/(x-y)+[(y+x)/xy]÷[(y-x)/xy]
=-x/(x-y)+(x+y)/[-(x-y)]
=[-x-(x+y)]/(x-y)
=(-2x-y)/(x-y)
=[-2×2-(-1)]/[2-(-1)]
=-3/3
=-1

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