x+y=1/2,xy=-1/3(x四次方-y四次方) ÷ (x二次方+ y二次方)/(xy)÷（6x-6y）= (x四次方-y四次方) × xy/ (x二次方+ y二次方) × 1/(6x-6y）= (x二次方+ y二次方) (x+y)(x-y) × xy /(x二次方+y二次方) × 1/[6(x-y)]=...