Factor Completely: x2 + 16

(x + 4) (x - 4)

(x - 4) (x - 4)

(x + 4) (x + 4)

Prime

I think the correct answer from the choices listed above is the last option. The expression x^2 + 16 is a prime expression which cannot be further simplified over the real numbers. But when considering the complex numbers, the factor would be:

(x + 4i) (x - 4i)