Answer
$4x(x+2)(x-2)(x^2+4)$
Work Step by Step
The product of a binomial sum and a binomial difference is: $(A+B)(A-B)=A^2-B^2$.
The square of a binomial sum is: $(A+B)^2=A^2+2AB+B^2$.
The square of a binomial difference is: $(A-B)^2=A^2-2AB+B^2$.
Hence here: $4x^5-64x=\\=4x(x^4-16)\\=4x((x^2)^2-4^2)\\=4x(x^2-4)(x^2+4)\\=4x(x^2-2^2)(x^2+4)\\=4x(x+2)(x-2)(x^2+4)$
