Question

x减y分之x乘x加y分之y的平方减去x的四次方减y的四次分之x的四次y除以x的二次加y的二次分之x的二次

Answer 1

原式=[x/(x-y)]*[y^2/(x+y)]-[x^4y/(x^2+y^2)(x^2-y^2)]/[x^2/(x^2+y^2)]

=xy^2/(x^2-y^2)-x^2y/(x^2-y^2)

=xy(y-x)/(x^2-y^2)

=-xy/(x+y).