分式通分三道题2xy/(x+y)的平方和x/x的平方-y的平方x-y/2x+2y和xy/(x+y)的平方2mn/4m的平方-9和2m-3/2m+3
问题描述：
分式通分三道题
2xy/(x+y)的平方和x/x的平方-y的平方
x-y/2x+2y和xy/(x+y)的平方
2mn/4m的平方-9和2m-3/2m+3
答
2xy/(x+y)^2和x/(x^2-y^2)2xy/(x+y)^2=2xy(x-y) / [(x+y)^2(x-y)]x/(x^2-y^2)=x(x+y)/[(x+y)^2(x-y)](x-y)/(2x+2y)和xy/(x+y)^2(x-y)/(2x+2y)=(x+y)(x-y)/[2(x+y)^2]xy/(x+y)^2=2xy/[2(x+y)^2]2mn/(4m^2-9)和(2m-3)/...