B) {-4, 4}
Proof:
Solve for x over the real numbers:
x^2 - 16 = 0
The left hand side factors into a product with two terms:
(x - 4) (x + 4) = 0
Split into two equations:
x - 4 = 0 or x + 4 = 0
Add 4 to both sides:
x = 4 or x + 4 = 0
Subtract 4 from both sides:
Answer: x = 4 or x = -4
