2xy/x平方-y平方-x/x+y+y/y-x,其中x=3、y=2 先化简再求值
题目
2xy/x平方-y平方-x/x+y+y/y-x,其中x=3、y=2 先化简再求值
答案
2xy/(x^2-y^2)-x/(x+y)+y/(y-x)=2xy/(x^2-y^2)-x/(x+y)-y/(x-y)=2xy/[(x-y)(x+y)]-x(x-y)/[(x-y)(x+y)]-y(x+y)/[(x-y)(x+y)]=[2xy-x(x-y)-y(x+y)]/[(x-y)(x+y)]=[2xy-x^2+xy-xy-y^2]/[(x-y)(x+y)]=-[x^2+y^2-2xy]/[(...
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