Question

Factor Completely: x2 + 16

Answer 1

i'm assuming you mean x^2, which makes the roots to this imaginary.

what level are you at? gradeschool? then you may have been asked to solve x^2-16. that's a difference of squares.

hint: (x-2)(x+2) expands to x^2-2x+2x-4=x^2-4 (note: 4=2^2)

Answer 2

Results in complex factors:
(x+4i)(x-4i)