[math][4(x-1/2y)(x+1/2y)]^2-(2x-3y)^2(2x+3y)^2-16y^2(2x-y)(2x+y)+(-4y^2)^2[/math]
[math][4(x^2-1/4y^2)]^2-(4x^2-9y^2)^2-16y^2(4x^2-y^2)+16y^4[/math]
[math][4x^2-y^2]^2-16x^4+72x^2y^2-81y^4-64x^2y^2+16y^4+26y^4[/math]
[math]16x^4-8x^2y^2+y^4-16x^4+8x^2y^2-49y^4[/math]
[math]-48y^4[/math]
