Answer:
x² + 8x + 16
Explanation:
(x + 4)² = (x + 4)(x + 4)
Each term in the second parenthesis is multiplied by each term in the first parenthesis, that is
x(x + 4) + 4(x + 4) ← distribute both parenthesis
= x² + 4x + 4x + 16 ← collect like terms
= x² + 8x + 16 ← perfect square trinomial