Answer:
[tex]\boxed{=2x(x^2+6y^2)}[/tex]
Step-by-step explanation:
Remember:
[tex](a+b)(a-b)=a^2-b^2\\\\a^3+b^3=(a+b)(a^2-ab+b^2)\\\\\\(x+2y)^3+(x-2y)^3\\\\=(x+2y+x-2y)((x+2y)^2-(x+2y)(x-2y)+(x-2y)^2)\\\\=2x(x^2+4xy+4y^2-(x^2-4y^2)+x^2-4xy+4y^2)\\\\=2x(x^2+6y^2)\\[/tex]
