This is the concept of polynomial functions, we are required to factor the polynomial of degree six given by:
9x^2-16y^6
let b=y^2
such that the expression becomes;
9x^2-16b^2
9x^2-12xb+12xb-16b^2
factoring the above we get:
3x(3x-4xb)+4b(3x-4b)
=(3x-4b)(3x+4b)
replacing b by y^2 we get:
(3x-4y^2)(3x+4y^2)