Respuesta :

x2 - 16, is the answer. The first one.

x^2 - 16 = (x)^2 - 4^2, difference of two squares :)
irspow
The difference of two squares is of the form:

(a^2-b^2)

I believe that they might just want you to select

(x^2-16) which factors to (x-4)(x+4)

But there is nothing mathematically incorrect in doing the same for:

(x^2-8) which factors to (x-√8)(x+√8)