Question

(x+2y)(x-2y)(x²+4y²)

Answer 1

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

Answer 2

$(x + 2y)( x - 2y)( {x}^{2} + 4 y {}^{2} ) \\ = (x { }^{2} - 4y {}^{2} )(x {}^{2} + 4y {}^{2} ) \\ =( x {}^{2} ) {}^{2} - (4 {y}^{2} ) {}^{2} \\ = x {}^{4} - 16y {}^{4}$