x/x-y*y2/x+y-x4y/x4-y4/x2/x2+y2
问题描述：
x/x-y*y2/x+y-x4y/x4-y4/x2/x2+y2
答
原式=(xy²)/(x+y)(x-y)-[x^4y/(x²+y²)(x²-y²)][(x²+y²)/x²]
=(xy²)/(x+y)(x-y)-x²y/(x²-y²)
=-xy(x-y)/(x+y)(x-y)
=-xy/(x+y)