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

问题描述:

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

16x^2y^2-(x^2+4y^2)^2
=(4xy)²-(x²+4y²)²
=(4xy+x²+4y²)(4xy-x²-4y²)
= - (x+2y)²(x-2y)²