:[x^2+y^2)-(x-y)^2+2y(x-y)]÷4y
=(x²+y²-x²+2xy-y²+2xy-2y²)÷4y
=(4xy-2y²)÷4y
=(2x-y)÷2
=4²÷2
=8
∴代数式值的立方根=³√8=2