(x^2+4y^2)^2-16x^2y^2

问题描述:

(x^2+4y^2)^2-16x^2y^2


=(x²+4y²)²-(4xy)²
=(x²-4xy+4y²)(x²+4xy+4y²)
=(x-2y)²(x+2y)²