就相当于用x^4-y^4除以(-x+y)(y^2+x^2)得到的结果,就是所求.(x^4-y^4)/[(-x+y)(y^2+x^2)]=[(x^2-y^2)(x^2+y^2)]/[(y-x)(y^2+x^2)]=(x^2-y^2)/(y-x)=(x+y)(x-y)/(y-x)=-(x+y)(y-x)/(y-x)=-(x+y)——答案：D...