[x^2-y^2(x-4y)(x+4y)-x^2-y^2(x-2y)^2]/[-(2xy)^2]
问题描述：
[x^2-y^2(x-4y)(x+4y)-x^2-y^2(x-2y)^2]/[-(2xy)^2]
[x^2y^2(x-4y)(x+4y)-x^2y^2(x-2y)^2]
答
[x²y²（x－4y）（x＋4y）－x²y²（x-2y）²]／[-（2xy）²]
＝x²y²（x²-16y²-x²＋4xy－4y²）／-4x²y²
＝20y²-4xy／4
＝5y²-xy