To solve the quadratic equation \( x^2 - 16 = 0 \), you can first rewrite it in a more standard form:
\[ x^2 = 16 \]
Next, take the square root of both sides:
\[ x = \pm 4 \]
This means the solutions are:
\[ x = 4 \quad \text{and} \quad x = -4 \]
Thus, the correct answer is:
x = 4 and x = -4.